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Pediatric Soft-Tissue Tumors Kamran Aflatoon, DO, Albert J. Aboulafia, MD, FACS, Edward F. McCarthy, Jr, MD, Frank J. Frassica, MD, and Alan M. Levine, MD Abstract Soft-tissue tumors in children repre- sent a heterogeneous group of lesions. The mass may be congenital, traumatic, inflammatory, benign neoplastic, or malignant neoplastic. Benign lesions may have limited growth, such as a lipoblastoma, or they may be ag- gressive, such as a desmoid tumor or extra-abdominal fibromatosis. Ap- proximately 6,000 new cases of soft- tissue sarcoma are diagnosed each year in adults, compared with 600 in children (<18 years), 1,2 or five to nine cases per million children annually. 3 Soft-tissue sarcomas are the fifth most common pediatric malignancy (4%) after leukemia (31%), central nervous system tumors (18%), lymphoma (12%), and neuroblastoma (8%). 4 In a review of more than 900 benign and malignant soft-tissue tumors in patients in the first two decades of life, Kransdorf 5,6 found that approximately 30% were vascular, 15% were neurogenic, and 14% were fibroblastic and myofibroblastic or were myogenic. Certain soft-tissue tumors occur more commonly in specific age groups and some in certain locations. For instance, malignant fibrous histiocytoma is the most frequent soft- tissue sarcoma in adults, whereas most types of tumor other than fibrohistiocytic and lipocytic are more common in children than in adults 7 (Table 1). Compared with those of adults, pediatric sarcomas usually have a higher histologic grade and greater metastatic potential and are more responsive to chemotherapy. 9 The clinical history is critical to establish a preliminary diagnosis. After a thorough history and physical examination, radiographic evaluation is used to narrow the differential diagnosis.Anylesion that cannot be differentiated by physical examination and radiographic findings is considered indeterminate and requires a biopsy 10 (Fig. 1). Clinical Presentation Typically, the child presents after dis- covery of a palpable mass by the parents or pediatrician. A recent trauma may have brought the mass to the parents’ attention. There may be associated symptoms, such as pain, joint contracture, or impaired function. When a soft-tissue mass is symp- tomatic, pain is the most common complaint. The history should include the nature and location of the pain, duration of symptoms, and any aggravating or alleviating factors, although this information may be difficult to elicit from a very young child. The parents may be able to provide additional information, but the onset of crying or wanting to be carried may be the only symptom. The most common soft-tissue tumors likely to present with pain in- Dr. Aflatoon is Instructor, Department of Ortho- paedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD. Dr. Aboulafia is Assistant Professor, Department of Orthopaedic Surgery, University of Maryland, Baltimore. Dr. McCarthy is Professor, Department of Pathol- ogy, and Professor, Department of Orthopaedic Surgery, Johns HopkinsUniversity Schoolof Med- icine. Dr. Frassica is Chairman and Professor, Department of Orthopaedic Surgery, Johns Hop- kins University School of Medicine. Dr. Levine is Director, Alvin and Lois Lapidus Cancer Institute, Department of Orthopaedic Oncology, Sinai Hospital, Baltimore. None of the following authors or the departments with whichthey areaffiliated hasreceived anything of value from or owns stock in a commercial com- pany or institution related directly or indirectly to the subject of this article: Dr. Aflatoon, Dr. Aboulafia, Dr. McCarthy, and Dr. Frassica. Dr. Levine, or the department with which he is affil- iated, serves as a consultant to or is an employee of Wright Medical. Reprint requests: Dr. Aflatoon, c/o Elaine P. Henze, Medical Editor, Department of Ortho- paedic Surgery, Johns Hopkins Bayview Medical Center, Room A672, 4940 Eastern Avenue, Baltimore, MD 21224-2780. Copyright 2003 by the American Academy of Orthopaedic Surgeons. Soft-tissue tumors in children (<18 years) are a heterogeneous group of lesions. Mass- es may be asymptomatic or associated with pain or discomfort. Although most lesions are benign, developing an appropriate differential diagnosis requires knowl- edge of the clinical and radiographic characteristics of tumors and tumorlike conditions in children. A thorough history and physical examination, followed by appropriate imaging studies, when indicated, can establish a correct diagnosis and help determine appropriate treatment recommendations. J Am Acad Orthop Surg 2003;11:332-343 332 Journal of the American Academy of Orthopaedic Surgeons clude hemangiomas and glomus tumors. Patients with hemangiomas typically complain of pain and discomfort after a period of standing or when the extremity is in a dependent position. Dilatation of venous cavities can cause muscular cramping and discomfort. When hemangiomas in- volve the gastrocnemius muscle, the child can present with toe walking. Symptoms may be relieved after the extremity is elevated or put at rest. These indications can be especially helpful in identifying hemangiomas involving the plantar aspect of the foot (Fig. 2). The character of the pain also may be helpful. Paroxysms of pain radiating from a lesion on exposure to cold temperatures suggest a glomus tumor. 11 Unlike glomus tumors in adults, those in children may be mul- tifocal. Pediatric glomus tumors commonly are in the superficial soft tis- Table 1 Relative Incidence of the Most Common Neoplastic Soft-Tissue Tumors 4,7,8 Occurrence (%) Tumor Type Examples Children Adults Vascular Hemangioma, arteriovenous malformation, lymphangioma, glomus tumor, angiomatosis, hemangiopericytoma 29 9 Neurogenic Neurofibroma, malignant peripheral nerve sheath, schwannoma, primitive neuroectodermal, clear cell sarcoma, neurothekeoma 15 9 Myogenic Rhabdomyosarcoma, leiomyosarcoma, leiomyoma, angiomyoma, epithelioid leiomyoma 14 5 Fibroblastic/ myofibroblastic Superficial fibromatosis, deep fibromatosis, fibrosarcoma, fibrous hamartoma 12 7 Fibrohistiocytic Fibrous histiocytoma, reticulohistiocytoma, xanthoma, malignant fibrous histiocytoma, dermatofibrosarcoma protuberans, angiomatoid fibrous histiocytoma 12 17 Lipocytic Lipoma, lipoblastoma, angiolipoma, spindle-cell lipoma, myolipoma, myelolipoma, atypical lipoma, liposarcoma 616 Other — 12 37 Child with a soft-tissue mass History and physical examination Radiography/MRI Indeterminate lesion Biopsy Malignant lesion Wide surgical resection Benign lesion Treatment based on symptoms Wide surgical reconstruction Determinate lesion (eg, hemangioma, lipoma, ganglion cyst) Superficial lesion or size ≤5 cm Deep lesion, lesion close to neurovascular bundles, or size >5 cm Treatment based on symptoms Neoadjuvant therapy (preoperative chemotherapy if tumor is sensitive [eg, rhabdomyosarcoma] and/or radiation therapy [eg, tumor is close to neurovascular bundles]) Figure 1 Presentation, diagnosis, and management of soft-tissue tumors. Figure 2 An 18-year-old man who had multiple operations on the medial and plantar as- pects of the foot for hemangioma presented with recurrence of the hemangioma and pain. Kamran Aflatoon, DO, et al Vol 11, No 5, September/October 2003 333 sues of the arms and legs rather than the subungual region, as in adults. 11 A history of trauma may be con- fusing rather than defining. When trauma brings a previously unrecog- nized mass to attention, diagnosis may be delayed because the mass is thought to be posttraumatic in origin (eg, hematoma, myositis ossificans, retained foreign body) (Figs. 3 and 4). The opposite also may be true: a posttraumatic lesion may simulate a malignant process and lead to unneces- sary anxiety and diagnostic studies if a patient fails to recall the causative traumatic episode. Physical Examination The physical examination should include an accurate assessment of the soft-tissue mass, including size, character, depth, and mobility. Lesions that are firm, deep (ie, below the fascia), and >5 cm in diameter are suspicious for malignancy. The shape and girth of the extremity should be measured, recorded, and compared with those of the opposite side. Le- sions suchaslymphangiomaor hemangioma may present with asymmetric enlargement of the involved extremity. 12,13 The regional and major lymph nodes should be palpated because rhabdomyosarcoma, synovial sarcoma, and epithelial sarcoma potentially can metastasize through the lymphatic system. Range of motion of the adjacent joints should be recorded because flexion contracture may be secondary to lesions such as desmoid tumor or intramuscular hemangioma. Some common lesions in pediatric patients have characteristic physical findings. These lesions often do not require additional imaging for diagnosis and may be treated symp- tomatically. Superficial hemangiomas frequently present with blue skin discoloration and subcutaneous swelling. The swollen area increases in size when the extremity is in a dependent position because it fills with blood. The patient may complain of pain with ambulation secondary to engorgement of the hemangioma. Subcutaneous lipomas account for 15% of adipose tumors in the first two decades of life. 14 Typically, the mass is doughy and nonmobile and does not cause discomfort. The most common site of involvement is the trunk. Subcutaneous lipomas usually do not grow, but when they do, magnetic resonance imaging (MRI) can help determine whether a lesion is a lipoma. Ganglia are not uncommon in pediatric patients; approximately 10% to 15% of all ganglia occur in the first two decades of life. 15 The mass is a well-defined, firm nodule composed of mucoid cyst surrounded by a fibrous capsule. Ganglia usually are located adjacent to or are attached to a joint capsule or tendon sheath. The dorsomedial aspect of the hand is the most common site. Diagnosis often can be confirmed by aspiration. Neurofibromas in individuals with von Recklinghausen’s neurofibromatosis are multiple, and growth of the lesions may be accelerated during pu- berty or pregnancy 16 (Figs. 5 and 6). The café-au-lait spots in prepubertal patients are smaller (approximately 5 mm) than those in adults (approximately 15 mm). 17 MRI of neurofibromas is not always required unless the patient complains of pain or the mass is enlarging. Deep lesions other than myositis ossificans require additional MRI scans. In pediatric patients, rhabdomyosarcoma (which accounts for 45% to 50% of all malignant soft-tissue sarcomas in children 18 ), synovial sarcoma, fibrous tumors, neurogenic tumors, fibrohistiocytic tumors, and desmoid tumors (or extra-abdominal fibromatosis) are deep to fascia and usually have a firm consistency. Malignant lesions are categorized into three grades (Table 2). Some soft- Figure 3 Lateral radiograph showing a firm mass inthe right upperextremity ofa 10-year- old boy. The parents could not recall any spe- cifictrauma.Themasswasdiagnosedasmyo- sitis ossificans circumscripta after computed tomography revealed a zonal calcification in the periphery and no calcifications in the center of the lesion. Figure 4 Two-centimeter mass on the right lower extremity of a 5-year-old boy with no history of trauma. Fat-saturated T2-weighted spin echo coronal MRI scan demonstrated a high signal intensity in the mass. Excisional biopsy revealed a retained thorn. Pediatric Soft-Tissue Tumors 334 Journal of the American Academy of Orthopaedic Surgeons tissue malignant tumors may be superficial, readily palpable, and small, but they should not be ignored. The most common are dermatofibrosarcoma protuberans (Fig. 7), epithelioid sarcoma, plexiform fibrohistiocytic tumor, and angiomatoid fibrous histiocytoma. Because of their activity level and tendency to play outdoors, children are prone to penetration injuries from sharp objects such as glass, wood, or thorns. Incomplete removal of a foreign body may leave material behind to induce future granulomatous reaction or abscess formation. 20 Foreign- body granuloma may lack the common findings of an infectious process and clinically and radiographically may mimic a soft-tissue sarcoma. 20,21 Radiographic Examination Plain radiographs and MRI are the most commonly used modalities for the evaluation of soft-tissue tumors. Other potentially useful imaging methods include computed tomography (CT) and ultrasound. Plain Radiographs Plain radiographs are critical in imaging any soft-tissue mass and are the first step in formulating the differential diagnosis. In some cases, radiographs provide more useful information than do advanced imaging techniques. They may occasionally reveal an underlying osseous process (eg, osteochondroma, osteomyelitis). Radiographs should be obtained in two orthogonal planes (usually anteroposterior and lateral). To accen- tuate soft-tissue details, the technician should obtain radiographs using a low-kilovolts peak (<50 kVp) technique (Fig. 8). The radiodensity of the lesion (ranging from radiolucency to radio- pacity) provides important clues. Deep lipoblastoma or other fatty tumors may present as a radiolucent mass. Air is rarely seen in soft-tissue tumors, except in cases of abscess. Radiodense foreign bodies within the soft tissues Figure 5 Café-au-lait spots in a 16-year-old boy with neurofibromatosis. Figure 6 Coronal T2-weighted MRI scan of the knee demonstrating neurofibroma along the course of the peroneal nerve (arrow) in a 14-year-old boy. Table 2 Grading for Pediatric Nonrhabdomyosarcoma Soft-Tissue Sarcoma 19 Grade Characteristic 1 Myxoid and well-differentiated liposarcoma Dermatofibrosarcoma protuberans Well-differentiated and infantile fibrosarcoma Well-differentiated and infantile hemangiopericytoma Extraskeletal myxoid chondrosarcoma Angiomatoid (malignant) fibrous histiocytoma Well-differentiated malignant peripheral nerve sheath tumor 2 Sarcomas (neither grade 1 nor 3) <15% area of necrosis <5 mitoses per high-power field No substantial nuclear atypia Not markedly cellular 3 Pleomorphic or round cell liposarcoma Mesenchymal chondrosarcoma Extraskeletal osteosarcoma Alveolar soft part sarcoma Malignant Triton tumor Marked atypia and cellularity Figure 7 Axial T1-weighted MRI scan of a subcutaneous, nonpalpable mass in the left leg of an 18-year-old man. Biopsy revealed a dermatofibrosarcoma protuberans. Kamran Aflatoon, DO, et al Vol 11, No 5, September/October 2003 335 can be easily detected on plain radiographs. Other findings include matrix mineralization, periosteal reaction, or cortical erosions. The calcification or mineralization pattern should be carefully studied. Chondroid matrix on plain radiographs appears as rings and arcs, whereas osteoid matrix presents as a cloudlike density (eg, extraskeletal osteosarcoma) or mature trabecular bone (eg, myositis ossificans), based on rate of growth. Radio- graphically, myositis ossificans presents with a well-developed zonal calcification pattern. In contrast with extraskeletal osteosarcoma, the calcification is more mature at the periphery than at the center of the lesion. Multiple small spotty calcifications are seen in 15% to 20% of synovial sarcomas. 22 The presence of phleboliths on plain radiographs is characteristic of vascular lesions, such as hemangioma 13 (Fig. 9). Ossification in the subcutaneous fat, muscles, tendons, and ligaments, forming a network of interconnecting bridges between adjacent bones and joints, is diagnostic of fibrodysplasia ossificans progressiva. 23 This hered- itary disease presents with a slowly progressive calcification of fibroblastic tissue that principally affects children younger than 10 years. The ossification leads to eventual ankylosis of the involved joints. Occasionally, a soft-tissue tumor may erode into the bone and be confused for a primary bone tumor. How- ever, a primary soft-tissue tumor presents with the epicenter outside the bone, whereas a primary bone tumor has an epicenter inside the medullary cavity. Periosteal new bone formation may or may not be present. Promi- nent periosteal reaction is commonly encountered in hypervascular soft- tissue neoplasms. 24 Solid periosteal reaction is more characteristic of a benign lesion, whereas interrupted periosteal reaction is associated with malignant soft-tissue tumors invading the bone. Radiographic evidence of initial erosion of the outer cortex of the bone, followed by beveling of the cortex toward the medullary cavity, in- dicates a soft-tissue lesion. Magnetic Resonance Imaging MRI is the most useful modality for imaging soft-tissue tumors because it can visualize the mass in multiple orthogonal views. It also provides a detailed anatomic picture of the mass, including location and the relation- ship to anatomic structures such as nerves, arteries, fascia, and periosteum. Soft-tissue masses vary in size and may arise in the skin, subcutis, muscle, or other deep soft tissues. In contrast with malignant bone tumors, most soft-tissue tumors, whether benign or malignant, tend to appear round or oval on MRI (Fig. 10); ex- ceptions include extra-abdominal desmoid tumors and dermatofibrosarcoma protuberans. Both benign and malignant soft-tissue tumors are en- capsulated, grow by centrifugal ex- tension, and tend to respect anatomic planes as they grow. This organized pattern may appear misleadingly benign to those unfamiliar with soft- tissue tumors. Although MRI does not provide histologic diagnosis, the characteristic features of a lesion on T1- and T2- weighted fat-suppression sequences can be highly specific. For example, using fat-suppression sequences, benign lipoblastoma, the most common fatty tumor in children, can be identified with a high degree of confi- dence because of signal attenuation: fat within the tumor has the same characteristics as subcutaneous fat. Malignant lesions (eg, myxoid) and infection tend to have low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. One distinctive feature of infection is the involvement of multiple fascial planes. Occasionally, malignant tumors contain areas of hemorrhage, which make the lesion appear heterogeneous. Tumors with low signal intensity on T1- and T2-weighted images, such as a desmoid tumor, are predominant- Figure 8 Anteroposterior low-kVp radiograph showing a soft-tissue mass (arrow) along the ulnar aspect of the right hand of a 10-year-old girl. Figure 9 Lateral radiograph showing multiple phleboliths in the upper extremity of a 14-year-old boy with hemangiomas. Figure 10 AxialT2-weighted MRI scandem- onstrating a spherical mass (fibrosarcoma [arrow]) in the medial aspect of the thigh of a 16-year-old girl. Pediatric Soft-Tissue Tumors 336 Journal of the American Academy of Orthopaedic Surgeons ly fibrous (Fig. 11). A desmoid tumor is a benign, nonencapsulated tumor that arises from the musculoapo- neurotic structures and tends to ex- tend along fascial planes. It has a local infiltrative growth pattern without potential for distant metastasis. The appearance of desmoid tumors on MRI is that of somewhat ill-defined intramuscular soft-tissue masses. Bony erosion and/or neurovascular encase- ment are common features. Desmoid tumors usually affect the muscles of the shoulder and hip. Such masses are isointense and do not demonstrate marked heterogeneity on T1-weighted images. However, on T2-weighted sequences, the tumors appear hyperin- tense with variable degrees of heterogeneity and fibrosis. 25 T2-weighted images are superior to T1-weighted images for demonstrating the ill- defined borders and infiltrative nature of desmoid tumors. The use of contrast medium such as gadolinium is helpful for differen- tiating cystic lesions from lesions that appear to be bright on T2-weighted images but have solid components (ie, tumor) within larger cystic areas. Malignant lesions are vascular and tend to enhance with the use of in- travenous contrast. A benign tumor, such as a hemangioma, cyst, or an abscess, characteristically shows contrast enhancement of the peripheral rim but no enhancement of the cavity because of its internal dysvascu- larity. Occasionally, the location of the mass, which may be better defined by MRI than by physical examination, may provide diagnostic clues. For instance, nodular masses along the tendon sheath with low signal intensity on both T1- and T2-weighted images suggest tenosynovial pigmented villonodular synovitis of the tendon sheath, whereas an intra-articular pedunculated mass with the same signal characteristics suggests intra- articular pigmented villonodular synovitis. Masses with fusiform ends that appear to be in continuity with a nerve are either schwannomas or neurofibromas. Table 3 lists selected soft-tissue masses, their presenting complaints, and radiographic findings. Biopsy The most important factor determin- ing the need for biopsy is certainty of the diagnosis after completion of the physical examination and imaging studies. Lesions such as lipoma, hemangioma, arteriovenous malformations, ganglion, myositis ossificans, plantar fibromatosis, and fibromatosis colli are considered determinate lesions and do not require biopsy. All other lesions that cannot be accurate- ly categorized and diagnosed are deemed indeterminate and require a biopsy. Preoperative imaging related to the tumor should be completed before biopsy because postoperative changes impair subsequent MRI evaluation of the mass. In addition, preoperative MRI helps the surgeon evaluate the extent of the tumor, lo- cate the optimal site for biopsy by avoiding areas that appear necrotic, and plan future surgery. The surgeon should be familiar with the indications for, as well as the advantages and disadvantages of, the various biopsy techniques. These techniques include needle (fine and core), excisional, and incisional. Inci- sional biopsy once was the preferred method. 26-28 However, compared with the incisional technique, needle biopsy has several advantages. It can be done in an outpatient setting with local anesthetic, is associated with a reduced incidence of infection and wound complications, affords the op- portunity to sample various portions Figure 11 A, A 16-year-old boy with a desmoid tumor involving the proximal tibia. B, On the T1-weighted axial MRI scan, the desmoid tumor appears dark. C, On the T2-weighted, fat-suppressed axial image, the tumor is mixed in signal intensity, with areas of dark and bright signal. Kamran Aflatoon, DO, et al Vol 11, No 5, September/October 2003 337 of the tumor, and may have less potential for local contamination by tumor cells. Excisional biopsy is rarely indicated for indeterminate lesions but may be considered for small (<1 to 2 cm) superficial masses located in anatomic areas amenable to adequate excision with tumor-free margins. The characteristics of the lesion and the extent of infiltration should be eval- uated based on MRI scans before excisional biopsy. An incisional biopsy may be done to obtain an adequate sample of the tumor, but several principles should be followed. A tourniquet can help decrease blood loss during biopsy and improve visualization of the surgical field. However, before inflation of the tourniquet, the extremity should be elevated above heart level to diminish its blood supply. Use of an Esmarch tourniquet, which would compress the tumor, is discouraged. A transverse incision for biopsy always should be avoided because it increases the extent of tissue loss at the time of definitive resection and may lead to contamination of unaffected muscle compartments. Creation of flaps at the time of biopsy should be avoided because more extensive dis- section allows microscopic tumor cells to spread to previously uncon- taminated areas. Necrotic areas should not be entered during biopsy because results would be of no diagnostic value. Damage to the local neurovascular structures may be prevent- ed by careful evaluation of the MRI scan. To prevent hematoma formation and tumor spread, meticulous hemo- stasis should be obtained at the con- clusion of the biopsy before closure. Frequently, a drain placed in line with the incision is necessary. For all incisional biopsies, intraop- erative frozen section should be done to ensure adequate quality of the tissue sample, which is crucial in cases with substantial areas of necrosis. However, the definitive surgical procedure usually is not done during the same procedure based on the result of frozen section alone. Complex cases requiring more extensive studies, such as immunohistochemical stain- ing and genetic analysis, may require a larger than usual amount of spec- imen and occasionally necessitate an open biopsy. Table 3 Selected Common Tumors Tumor Type Presentation Benign neoplastic Superficial hemangioma Superficial blue mass, occasional pain Deep hemangioma Muscular pain, enlarging mass Digital fibromatosis Nonpainful mass, usually dorsal or on the sides of the long, ring, small digits; first year of life Fibrous hamartoma of infancy Nonpainful, small, rapidly growing mass in dermis and subcutis Schwannoma Slowly growing mass, no pain except with larger ones Glomus Paroxysm of pain radiating from a lesion, cold sensitive Neurofibroma Slowly growing nonpainful mass Infantile fibromatosis (desmoid) Patients usually age <8 years; nonpainful mass, rapid growth Fibrous histiocytoma Solitary slowly growing nodule Myofibroma (MF) and myofibromatosis (MFT) MF: single mass in the dermis or subcutaneous, <2 cm in diameter, nonpainful; MFT: multiple lesions Fibromatosis colli Nodule in the sternocleidomastoid (SCM) muscle presenting as torticollis; rapid growth in the first few months, then stationary Lymphangioma Extremity heaviness, asymmetric enlargement of one extremity Nonmalignant Foreign body granuloma Gradually growing mass in upper or lower extremity Heterotopic ossification Growing mass in an active child, may provide history of trauma Malignant Dermatofibrosarcoma protuberans Slow and persistent growth over a long period of time, most commonly in the trunk and proximal extremities Malignant peripheral nerve sheath tumor Patients with neurofibromatosis 1 at increased risk, present with a painful neurofibroma Synovial sarcoma Palpable mass in extremity (generally asymptomatic) Infantile fibrosarcoma Rapidly growing mass in the first year of life, mostly in extremities Rhabdomyosarcoma Upper or lower extremity, rapidly growing nonpainful mass, most common in lower extremity Pediatric Soft-Tissue Tumors 338 Journal of the American Academy of Orthopaedic Surgeons Minimally invasive techniques include fine-needle aspiration biopsy and core needle biopsy. Fine-needle aspiration biopsy is done by multiple aspirations through the tumor using a 23- to 27-gauge needle. It should be done only in a center that has pa- thologists with extensive experience with the technique. 29,30 Under even optimal circumstances, fine-needle aspiration is less effective than core biopsy, especially for fibrous lesions Physical Findings Radiographic Findings Benign neoplastic Compressible mass with blue skin discoloration Bright on T1- and T2-weighted MRI; may have phlebolith on radiograph None Bright on T1- and T2-weighted MRI; may have phlebolith on radiograph Rarely >2 cm, hemispheric or dome-shaped, with shiny skin surface Low signal on T1- and T2-weighted MRI Freely movable, rarely fixed to the fascia or muscle Low signal on T1- and T2-weighted MRI Freely movable except in the long axis of the nerve Low signal on T1-weighted MRI, high signal on T2-weighted MRI Lesion found in the subcutis of the extremity High signal on T1- and T2-weighted MRI Usually multiple, may present with superficial and deep lesions Low signal on T1-weighted MRI, high signal on T2-weighted MRI Deeply seated, poorly circumscribed solitary mass in muscle or fascia; may infiltrate muscles and nerves as it grows and cause pain and functional disturbance Inhomogeneous signal intensity on MRI; poor margin- ation; involvement of neurovascular bundles Elevated or pedunculated lesions <2 cm; overlying skin is red to red-brown secondary to hemosiderin Low signal on T1- and T2-weighted MRI MFT has multiple nodules and involvement of muscle, bone, and internal organs (lung, heart, gastrointestinal system) Soft-tissue swelling; multiple circumscribed lytic bony lesions, some marginal sclerosis; no cortical violation Firm mass in the SCM close to the sternal or clavicular portion; should not be confused with acquired (traumatic) torticollis Low signal on T1- and T2-weighted MRI Asymmetric enlargement of the extremity Multiloculated osteolytic lesions in bone; lymphangio- gram localizes blind pouch Nonmalignant Occasionally painful, may present with erythema Some materials are radiodense and easily seen on radiographs; ultrasound may be helpful in some cases Hard mass most commonly seen in the anterior thigh Zonal pattern of calcification with more peripheral mature bone compared with center of mass Malignant Firm plaquelike lesion with red to blue discoloration of the surrounding skin When subcutaneous, MRI shows more tissue involvement than clinical picture Large, deeply situated mass commonly associated with major nerve trunk Low signal on T1-weighted MRI, high signal on T2-weighted MRI; MRI can identify nerve trunk Deep mass, close proximity to major joints Low signal intensity on T1-weighted MRI, high signal on T2-weighted MRI Size from a few to >20 cm Inhomogeneous low signal on T1-weighted MRI, high signal on T2-weighted MRI Solid deep mass; lymph nodes should be inspected for evidence of metastasis Inhomogeneous low signal on T1-weighted MRI, high signal on T2-weighted MRI Kamran Aflatoon, DO, et al Vol 11, No 5, September/October 2003 339 and those that require accurate grading to determine the best treatment. The larger core needle (1 mm in diameter) provides a sliver of tissue for microscopic analysis. In an outpatient setting with the patient under local anesthesia, the needle is passed per- cutaneously several times through the tumor. To improve the accuracy of the sample, necrotic areas should be avoided. Such areas can be identified before biopsy by careful evaluation of the MRI scan. CT or ultrasound guid- ance can be used for deep lesions. Usu- ally there is sufficient tissue for specific histochemical stainingandgrading. Diagnostic accuracy approaches 90% with core needle biopsy. 31 Staging A patient with a soft-tissue sarcoma should be staged before initial treatment. The presence or absence of skeletal or visceral metastases should be assessed during this evaluation phase. Because the lungs are the most common site for metastasis, CT scans of the chest are essential. Tumors such as rhabdomyosarcoma, epithelial sarcoma, or synovial sarcoma may metastasize to the regional lymph nodes. Suspicious enlargement of the local and regional nodes should be eval- uated clinically and with MRI or CT scans. However, even when the clinical examination and radiographic findings are negative for lymphatic metastasis, biopsy may reveal the presence of micrometastasis to the regional lymph nodes. 32,33 Jager et al 34 found a 7% incidence of skeletal metastasis in patients with soft-tissue sarcoma (8/109 patients), and Kim et al 35 reported a 4% incidence (1/23 patients). The presence of skeletal metastasis should be ini- tially investigated with bone scan and plain radiographs and, when indicated, with MRI. 36 Bone marrow aspiration is indicated as part of the staging for patients with rhabdomyosarcoma. 31 Management Management of a soft-tissue tumor is based on its natural history, tendency for local recurrence, and potential for or presence of distant metastasis. The choice of nonsurgical or surgical approach is dictated by tumor type. The appearance of lipoma on MRI (the same signal characteristics as subcutaneous fat on all sequences) is so characteristic that, in most cases, biopsy is not needed to establish the diagnosis with reasonable certainty. 35,37 Although the characteristic appearance of lipomas is well described, MRI also is useful in identifying less common lipomalike variants that are unique to children younger than 5 years and that are predominantly seen as fat in MRI but exhibit variable amounts of inhomogeneity. Wide local excision is used to treat lipoblastoma and lipoblastomatosis. Asymptomatic hemangiomas can simply beobserved.Those thatare symp- tomatic (pain or increasing deformity) can be treated by surgical excision if function will not be severely impaired or by embolization and/or direct injection in areas in which surgical excision will have notable morbidity. Some tumors, such as hemangiomas or arteriovenous malformations, can be managed with minimally invasive treatment. Injection of ethanol into the hemangioma cavity may oblit- erate the tumor mass, although failure (ie, local recurrence) rates may be morethan50%. 38 An arteriovenous malformation may be managed by plac- ing coils in the major feeding vessels. Marginal resection may be used to treat most benign tumors, such as a benign neurofibroma or lipoblastoma. In this type of resection, the tumor is removed but the inflammatory zone around the tumor, with potential microscopic tumor, is left. For malignant tumors (eg, rhabdomyosarcoma, synovial sarcoma), the surgical approach is to achieve wide resection, which involves removal of the tumor, its reactive zone, and a rim of healthy tissue around it. However,some malignant soft-tissue tumors in children require multimodality therapy. Desmoid Tumor Desmoid tumors are not truly malignant because they do not exhibit distant metastases; however, patients frequently have local recurrences that may be difficult to manage. There is no consensus regarding preferred treatment. Several protocols have been recommended, including radiation, surgery, chemotherapy, benign neglect, and combinations thereof. 39-42 The most commonly used therapies are surgical resection and radiation. Nei- ther Merchant et al 43 nor Spiegel et al 44 recommended radiation therapy alone to treat desmoid tumors in pediatric patients. Spiegel et al 44 showed a better result with wide surgical resection and adjuvant chemotherapy than with radiation therapy alone. Similarly, Merchant et al 43 showed 77% failure with radiation therapy alone (10/13 patients). Surgical resection is done with the intent of achieving a wide or, in some cases, a radical margin. With negative margins, local control is improved with adjuvant radiation. However, high rates of local recurrence, even in the setting of negative surgical margins and the use of adjuvant radiation, have created interest in developing nonsurgical and non–radiation-based treatments. This is especially important for skeletally immature patients because radiation may be associated with risks of growth disturbance, contractures, and secondary malignancies. 44 Alternative therapies include observation, hormones, hormone an- tagonists, cyclooxygenase inhibitors, interferon alpha, and cytotoxic chemotherapy. The use of vinblastine and methotrexate has been reported to control disease in most children with desmoid tumors who were not amenable to surgical or radiation treatment. 45 Future treatment may fo- cus on the molecular basis of fibro- blast mitogenesis. 46 Pediatric Soft-Tissue Tumors 340 Journal of the American Academy of Orthopaedic Surgeons Synovial Sarcoma Synovial sarcoma is the second most common malignant soft-tissue tumor in pediatric patients. 46,47 Wide surgical resection with adjuvant radiation has a 5-year failure-free survival rate of approximately 75%. 47-49 The usefulness of chemotherapy in conjunction with surgery and radiation therapy for long-term survival remains controversial. 47,49,50 Rhabdomyosarcoma Rhabdomyosarcoma is more common in the lower extremity (approximately 19% of all cases) than upper extremity 32,51 and has multiple histologic subtypes with distinct prognoses. The occurrence of the two subtypes most commonly seen in the extremities, embryonal and alveolar, is age dependent. Embryonal rhabdomyosarcoma occurs more commonly in children, whereas alveolar rhabdomyosarcoma is more commonly found in adults. 52 Another subtype, pleomorphic rhabdomyosarcoma, is more common in adults aged 21 to 81 years (mean age, 51 years). 53 Gene alteration for most embryonal rhabdomyosarcoma has been determined to be a deletion of chro- mosome band 11p15.5. The gene al- terationinmostalveolarrhabdomyo- sarcoma has been determined to be a chromosomal translocation t(2;13) (q35;q14) involving the PAX3 gene on band 2q35 and the FKHR gene on band 13q14. 54,55 The treatment protocol for a patient with rhabdomyosarcoma is based on several factors, the most important of which is presence or absence of distant metastasis. Current treatment of children with rhabdomyosarcoma that has metastasized beyond the regional lymph nodes in- cludes multiagent chemotherapy and radiation therapy. 32,56-59 Such patients have a 5-year survival rate, ranging from 20% to 30%, 32,56-59 based on the histologic subtype of the tumor. The Intergroup Rhabdomyosar- coma Study IV has shown that the following factors are statistically significant predictors of failure-free survival in patients without distant metastasis: presence of a tumor in local lymph nodes, tumor size, and invasiveness of the tumor (ie, involvement of the neurovascular bundles, multiple compartments) 32 (Table 4). Patients with nonmetastatic rhabdomyosarcoma have a mean 3-year overall failure-free survival rate of 71% when treated with multimodality therapy, including wide surgical resection, intensive multiagent chemotherapy, and radiation therapy. 56,60 Radiation therapy is recommended for patients with re- sidual tumor at the site of resection, involvement of local lymphatics, and alveolar or undifferentiated rhabdomyosarcoma. 61,62 Summary Evaluation of the pediatric patient with a soft-tissue mass can be chal- lenging. To formulate a differential diagnosis and, ultimately, diagnose a presenting lesion, the clinician should have an organized and systematic approach to the evaluation. There are five basic categories of soft-tissue masses: congenital, traumatic, inflammatory, benign neoplastic, and malignant neoplastic. Some lesions may re- semble each other, and the diagnosis may be indeterminate without doing a biopsy. Before biopsy, the clinician should obtain all relevant clinical and radiographic diagnostic information. To optimize patient outcome, biopsy should follow all the principles of on- cologic surgery. Most traumatic and benign soft- tissue lesions can be managed by either observation or marginal excision. Survival rates for patients with malignant sarcomas continue to improve because of advances in chemotherapy and use of multimodality therapy (eg, radiation therapy, surgical resection). To optimize their management and survival, patients with malignant sarcomas should be treated at centers with special interest in these conditions as well as with the resources to render multimodality therapy and provide appropriate follow-up for de- tecting recurrence or metastasis after resection. Table 4 Statistically Significant Predictors of Failure-Free Survival 32 Tumor Characteristic Measurement Statistical Difference Number of lymph nodes affected 0 versus 1 or more P < 0.001 Size <5 cm versus ≥5cm P = 0.04 Invasiveness Superficial or single versus deep or multiple P < 0.001 Kamran Aflatoon, DO, et al Vol 11, No 5, September/October 2003 341 [...]... Benign soft-tissue tumors in a large referral population: Distribution of specific diagnoses by age, sex, and location AJR Am J Roentgenol 1995;164:395-402 Harms D: Soft tissue sarcomas in the Kiel Pediatric Tumor Registry Curr Top Pathol 1995;89:31-45 Dillon P, Maurer H, Jenkins J, et al: A prospective study of nonrhabdomyosarcoma soft tissue sarcomas in the pediatric age group J Pediatr Surg 1992;27:... soft tissue sarcomas: Results of a clinicohistopathologic correlation in a series of 163 cases Cancer 1984;53:530-541 Weston WJ: Thorn and twig-induced pseudotumours of bone and soft tissues Br J Radiol 1963;36:323-326 Aflatoon K, Aboulafia AJ, McCarthy EF Jr, Frassica FJ: Soft tissue mass in a 5-year-old boy Clin Orthop 2003;411: 348-354 Sanchez Reyes JM, Alcaraz Mexia M, Quinones Tapia D, Aramburu JA:... Weiss SW: Benign fibrous tissue tumors, in Enzinger FM, Weiss SW (eds): Soft Tissue Tumors, ed 3 St Louis, MO: Mosby-Year Book Inc, 1995, pp 165-199 Shives TC: Biopsy of soft-tissue tumors Clin Orthop 1993;289:32-35 Simon MA, Biermann JS: Biopsy of bone and soft-tissue lesions J Bone Joint Surg Am 1993;75:616-621 Liu K, Layfield LJ, Coogan AC, Ballo MS, Bentz JS, Dodge RK: Diagnostic accuracy in fine-needle... Combination chemotherapy using vinblastine and methotrexate for the treatment of progressive desmoid tumor in children J Clin Oncol 1998;16:3021-3027 Shields CJ, Winter DC, Kirwan WO, Redmond HP: Desmoid tumours Eur J Surg Oncol 2001;27:701-706 Andrassy RJ, Okcu MF, Despa S, Raney RB: Synovial sarcoma in children: Surgical lessons from a single institution and review of the literature J Am Coll Surg 2001;192:305-313... children Clin Imaging 2000;24:257-262 Yoshikawa H, Myoui A, Ochi T, et al: Bone metastases from soft tissue sarcomas Semin Musculoskelet Radiol 1999;3: 183-190 Reiseter T, Nordshus T, Borthne A, Roald B, Naess P, Schistad O: Lipoblastoma: MRI appearances of a rare paediatric soft tissue tumour Pediatr Radiol 1999;29:542-545 Beham A, Fletcher CD: Intramuscular angioma: A clinicopathological analysis of 74... RA: Desmoid tumor: Prognostic factors and outcome after surgery, radiation therapy, or combined surgery and radiation therapy J Clin Oncol 1999;17:158-167 Journal of the American Academy of Orthopaedic Surgeons Kamran Aflatoon, DO, et al 43 44 45 46 47 48 49 50 51 Merchant TE, Nguyen D, Walter AW, Pappo AS, Kun LE, Rao BN: Long-term results with radiation therapy for pediatric desmoid tumors Int J Radiat... Radiol 1997;26:671-673 Bridges AJ, Hsu KC, Singh A, Churchill R, Miles J: Fibrodysplasia (myositis) ossificans progressiva Semin Arthritis Rheum 1994;24:155-164 Moser RP Jr, Parrish WM: Radiologic evaluation of soft tissue tumors, in Enzinger FM, Weiss SW (eds): Enzinger and Weiss’s Soft Tissue Tumors, ed 4 St Louis, MO: Mosby-Year Book Inc, 2001, pp 45-102 Hartman TE, Berquist TH, Fetsch JF: MR imaging of... 5, September/October 2003 52 53 54 55 56 57 Maurer HM: Biology and therapy of pediatric rhabdomyosarcoma J Clin Oncol 1995;13:2123-2139 Weiss SW, Goldblum JR: Rhabdomyosarcoma, in Weiss SW, Goldblum JR (eds): Enzinger and Weiss’s Soft Tissue Tumors, ed 4 St Louis, MO: Mosby, 2001, pp 785-836 Furlong MA, Mentzel T, FanburgSmith JC: Pleomorphic rhabdomyosarcoma in adults: A clinicopathologic study of... 1992;27: 241-245 Felgenhauer J, Hawkins D, Pendergrass T, Lindsley K, Conrad EU III, Miser JS: Very intensive, short-term chemotherapy for children and adolescents with metastatic sarcomas Med Pediatr Oncol 2000; 34:29-38 Frassica FJ, Thompson RC Jr: Evaluation, diagnosis, and classification of benign soft-tissue tumors Instr Course Lect 1996;45:447-460 Tsuneyoshi M, Enjoji M: Glomus tumor: A clinicopathologic... JJ, Woodruff JM, Brennan MF: Core needle biopsy for diagnosis of extremity soft tissue sarcoma Ann Surg Oncol 1997;4:425-431 Neville HL, Andrassy RJ, Lobe TE, et al: Preoperative staging, prognostic factors, and outcome for extremity rhabdomyosarcoma: A preliminary report from the Intergroup Rhabdomyosarcoma Study IV (1991-1997) J Pediatr Surg 2000;35:317-321 Khirwadkar N, Dey P, Das A, Gupta SK: Fine-needle . Soft-Tissue Tumors 336 Journal of the American Academy of Orthopaedic Surgeons ly fibrous (Fig. 11). A desmoid tumor is a benign, nonencapsulated tumor that arises from the musculoapo- neurotic structures. may be helpful. Paroxysms of pain radiating from a lesion on exposure to cold temperatures suggest a glomus tumor. 11 Unlike glomus tumors in adults, those in children may be mul- tifocal should be done to ensure adequate quality of the tissue sample, which is crucial in cases with substantial areas of necrosis. However, the definitive surgical procedure usually is not done during

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