21 -CYSTS,TUMORS,TUMORLIKE LESIONS OF SPINAL CORD and SPINE .

C H A P T E R Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord Extradural Tumors, Cysts, and Tumorlike Mass Benign Tumors Cysts and Other Benign Tumorlike Masses Malignant Tumors Intradural Extramedullary Tumors, Cysts, and Tumorlike Masses Benign Tumors Cysts and Other Benign Tumorlike Masses Malignant Tumors Intramedullary Tumors, Cysts, and Tumorlike Masses Tumors Cysts and Tumorlike Masses Spinal cord tumors and tumorlike masses are traditionally classified by location into three categories,1,2 (see box, p 877, top left) as follows: Extradural lesions (lesions of the osseous spine, epidural space, and paraspinous soft tissues) Intradural extramedullary lesions (lesions that are inside the dura but outside the spinal cord) Intramedullary lesions (spinal cord cysts and tumors) EXTRADURAL TUMORS, CYSTS, AND TUMORLIKE MASSES Extradural masses occur outside the spina and typically arise from the osseous spine, intervertebral disks, and adjacent soft tissues Genera imaging hallmarks of an extradural mass lesion are focal displacement of the thecal sac and its contents away from the mass (Fig 21-1, A) Myelography shows extrinsic compression of the thecal sac Myelographic "block" (sometimes the redundant term, complete block, is used) occurs with large lesions and is seen as a displaced thecal sac with obliterated subarachnoid space and compressed spinal cord The border between the lesion and the head of the contrast column has a poorly delineated "feathered" appearance (Fig 21-1, B and C).2 MR scans clearly show the dura draped over the mass (Fig 21-1, D) In some cases a crescent of displaced epidural fat can be seen capping the lesion (see Fig 21-16, B and C) The most common benign extradural masses are degenerative and traumatic lesions such as disk herniations, osteophytes, and fractures (see Chapter 20) Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 877 Classification of Spine Lesions by Anatomic Compartment Extradural masses Location: outside thecal sac Tissues: osseous spine, epidural space, paraspinous soft tissues Examples: herniated disk, spondylitic spurs, fractures, metastases Classic myelogram appearance: thecal sac extrinsically compressed; if block, interface between lesion and contrast column is poorly defined with "feathered" appearance at level of obstruction Intradural extramedullary masses Location: inside thecal sac but outside cord Tissues: nerve roots, leptomeninges, CSF spaces Examples: nerve sheath tumors, meningiomas Classic myelogram appearance: intradural filling defect outlined by sharp meniscus of contrast; spinal cord deviated away from mass; ipsilateral subarachnoid space enlarged up to mass Intramedullary masses Location: inside spinal cord Tissues: cord parenchyma, pia Examples: astrocytorna, hydrosyringomyelia Classic myelogram appearance: diffuse, multisegmental smoothly enlarged cord with gradual subarachnoid space effacement The most common neoplastic extradural mass is metastasis In this section, we consider neoplasms, cysts, and tumorlike masses of the osseous spine and paraspinal soft tissues Benign Tumors Hemangioma Pathology Vertebral hemangiomas (VHs) are slow-growing benign primary neoplasms of capillary, cavernous, or venous origin The most common histologic type is cavernous hemangioma These lesions are composed of mature thin-walled vessels and large blood-filled endothelial-lined spaces.3,4 The dilated vessels are interspersed among longitudinally oriented trabeculae that appear reduced in number but are thicker in diameter.5 VHs vary from predominantly fatty lesions (Fig 21-2, A) to hemangiomas comprised largely of vascular stroma with little or no adipose tissue (see box, right).4 Incidence, age, and gender Hemangiomas are found in 10% to 12% of all autopsies, making VH the most common benign spinal neoplasm.3 The peak incidence is in the fourth to the sixth decades Asymptomatic hemangiomas occur equally in men and Fig 21-1 Imaging features of an extradural mass A, Anatomic diagram, lateral view, depicts a pathologic compression fracture with spinal cord compression The dura (small arrows) and spinal cord (large arrows) are displaced The subarachnoid space is filled with intrathecal contrast (gray area: open arrows) Gradual tapering of the contrast column with a "feathered" appearance (double arrows) is present Cephalad flow of contrast is blocked by the compressive lesion, and the CSF distal to the obstruction (shown in white) is un opacified Continued Hemangioma Vascular/fatty stroma with sparse but thick trabeculae Usual location: part or all of vertebral body Common incidental finding at MR (round "white spot" on T1WI), CT ("polka dot" vertebral body) Most are asymptomatic; can expand, cause pathologic fracture, epidural mass with cord compression Differential diagnosis: fatty marrow replacement women but there is a female predominance with symptomatic lesions Location Nearly 75% of all osseous hemangiomas occur in the spine.3 The lower thoracic and lumbar regions are the most common sites Multiple lesions 6,7 are seen in 25% to 30% of cases Most hemangiomas are located in the vertebral body Lesion extent is variable (Fig 21-2) Some lesions involve only part of the vertebral body, whereas others affect the entire medullary space Hemangi- 878 PART FIVE Spine and Spinal Cord Fig 21-1, cont’d B and C, Myelographic findings of extradural mass are shown Lateral view (B) shows an extradural mass effect (small arrows) with block of contrast flow (large arrow) AP view (C) in another case shows the ill-defined "feathered" appearance at the head of the contrast column (arrows), caused by an extradural mass with block D, Sagittal T2-weighted MR scan in a patient with metastatic breast carcinoma and a high signal intensity pathologic compression fracture (large arrow) shows the dural displacement (open arrows) that is characteristic of an extradural mass effect oma isolated to the neural arch is uncommon, but 10% to 15% of vertebral body VHs have concomitant involvement of the posterior elements (Fig 21-3).3 Most epidural hemangiomas occur secondarily as extensions of expanding intraosseous lesions.8 Completely extraosseous hemangioma is rare, accounting for only 1% to 2% of all VHs Clinical presentation and natural history Approximately 60% of VHs are asymptomatic lesions that are discovered incidentally on imaging studies.6 Pain is the presenting complaint in 20%.6 In most patients with VHs, back pain is related to other etiologies, not the hemangioma.4 Approximately 20% of VHs present with progressive neurologic deficits or symptoms of acute spinal cord compression Progression of an asymptomatic or painful lesion to a neurologically symptomatic one is rare, occurring in less than 5% of cases.6 VHs usually become symptomatic when pathologic compression fracture or epidural extension occurs Symptom onset is often, although not invariably, acute and is probably secondary to hemorrhage with sudden increase in mass effect.8 Pregnancy may exacerbate some lesions.8a Some authors report fatty VHs are usually clinically inactive, whereas those with imaging findings suggesting a more vascular stroma have the potential to cause spinal cord compression.4 Imaging findings Plain film radiographs show lytic foci with honeycomb trabeculation or thick vertical striations.5 NECT scans show a lucent lesion with typical "polka dot" densities in the medullary space that represent the coarsened vertical trabeculae characteristic of VHs VHs range in size from small, localized lesions (Fig 21-2, C) to hemangiomas that involve the entire vertebral body (Fig 21-2, B) Myelography or CT-myelography in cases with extraosseous extension show an extradural mass (Fig 21-4, B) Angiographic findings vary from normal to intense hypervascular stain on selective segmental spinal angiograms.4 MR imaging findings vary Most VHs are seen as round, relatively well-delineated vertebral body lesions that are high signal intensity on both T1- and T2-weighted sequences (Fig 21-4, A) The hyperintense stroma surrounds foci of very low signal inten- Chapter 21 879 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord Fig 21-2 Pathology and imaging findings of typical vertebral, body hemangiomas A, Gross pathology specimen shows a classic hemangioma Note marrow replacement by fatty stroma (large arrows) and fewer but strikingly thickened trabeculae (small arrows) B and C, Axial CT scans show typical hemangiomas This hemangioma (B) (large arrows) occupies nearly the entire vertebral body Note "polka-dot" appearance caused by the thickened trabeculae seen in axial section (open arrows) Post-myelogram CT scan (C) in another patient shows a very small incidental focal hemangioma (arrows) (A, From archives of the Armed Forces Institute of Pathology.) sity, representing the thickened vertical trabeculae (Fig 21-3, B) Some VHs are predominately low signal on T1WI These lesions often enhance following contrast administration and may be associated with an extradural soft tissue mass Histologically, these VHs contain predominately vascular rather than fatty stroma.4 Differential diagnosis The major differential diagnostic consideration on MR scans is focal fatty marrow replacement or hemangioma VHs typically have high signal intensity on both T1- and T2WI, whereas fatty lesions become hypointense on standard T2-weighted spin echo images VHs that are mostly fatty can be indistinguishable from fatty marrow replacement; both are clinically indolent lesions that are common causes of vertebral body "white spots" seen incidentally on MR scans Fat suppression sequences are helpful in distinguishing fatty marrow replacement from VHs that are primarily vascular Osteoid osteoma (Table 21-1) Pathology Osteoid osteoma is a benign skeletal neoplasm that has a central nidus of interlacing osteoid and woven bone mixed with loose fibrovas- Fig 21-3 Hemangioma that involves the vertebral body, pedicle, and articular pillar of C5 A, Axial NECT scan shows the lesion (arrows) (Courtesy M Fruin.) Continued 880 PART FIVE Spine and Spinal Cord Fig 21-3, cont'd B, Axial T2-weighted MR scans show the high signal stroma (arrows) (Courtesy M Fruin.) Fig 21-4 This 42-year-old man had a 48-hour history of back pain and leg weakness followed by sudden onset of paraplegia and incontinence A, Sagittal postcontrast T1-weighted MR scan shows a high signal lesion in the vertebral body (curved arrow) and an extradural soft tissue mass with enhancing rim (straight arrows) that is compressing the conus medullaris B, Post-myelogram CT scan with reformatted sagittal image shows the extradural mass (arrows) Surgery disclosed extradural hemangioma with acute hemorrhage cular stroma.9,10 Osteoid osteomas are sharply demarcated from surrounding bone and are surrounded by varying degrees of osteosclerosis.9 Associated paraosseous soft tissue masses occasionally occur with extremity lesions but have not been reported in the spine.11 The nidus of an osteoid osteoma rarely exceeds 1.5 to 2.0 cm in diameter9; larger lesions are typically categorized as osteoblastoma, although the distinction between these two entities is not always clear.10 Incidence, age, and gender Osteoid osteoma is a relatively common lesion that accounts for approxi- mately 12% of benign skeletal neoplasms.9 Osteoid osteomas represent approximately 6% of benign spine tumors.5 Patients with osteoid osteoma are usually young Osteoid osteomas are rarely seen beyond 30 years of age.5 Approximately half of all cases present between the ages of 10 and 20 years.9,10 The male:female ratio is 2-4:1.5,9,10 Location Osteoid osteoma may occur in virtually any location; the lower extremity is the site for more than half of all lesions Approximately 10% of osteoid osteomas are found in the spine The most commonly Chapter 21 Tumors, Cysts, and Tumorlike Lesions of the Spine and Spinal Cord 881 Table 21-1 Benign osseous tumors and tumorlike lesions of the spine Lesion Location Incidence Age Hemangioma Vertebral body (T, L>C) Most common Osteoid osteoma Neural arch (L, C>T) Osteoblastoma Neural arch (C>L, T; sacrum) Common (10% in 10 to 20 years Dense sclerosis, lucent spine) nidus, lesion