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ROLE OF IMAGING IN ADRENAL GLAND • The adrenal glands are known to be a frequent site of disease and one of the most common pathologic involvement of the adrenal glands is neoplastic in nature A variety of modalities can effectively image the adrenals, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI) and scintigraphy By far, the multisequential imaging capabilities of CT supersede the rest in establishing a definitive diagnosis in adrenal mass, however imaging with MRI and US partaking a complimentary role • • It is crucial for the radiologist to be able to diagnose and differentiate adrenal masses on imaging Herein, we aim to review the common as well as the uncommon adrenal masses encountered in one’s practice Clinical Indications for Adrenal MRI • As defined by the ACR-SAR-SPR Practice Parameters: •  Detection of suspected pheochromocytoma and functioning adrenal adenoma •  Characterization of indeterminate lesions detected with other imaging modalities •  Staging of malignant adrenal neoplasms •  Detection and characterization of congenital anomalies Institutional Adrenal MRI Protocol • Axial T2-weighted imaging • Coronal T2-weighted imaging • Axial pre in and opposed phase imaging • Coronal in and opposed phase imaging • Axial DWI sequenceAxial pre fat suppressed • Axial postcontrast• Arterial – 25 sec• Portal – 60 sec• Venous – 95 sec• Delayed – • Axial postcontrast in phase and opposed phase imaging MR Imaging • Utility of specific imaging sequences and quantitative variables for optimal characterization of an adrenal lesion •  Chemical shift imaging - assessment for fat •  Calculation of adrenal-to-spleen chemical shift ratio, signal-intensity index •  Emerging techniques •  Dynamic contrast enhancement •  Diffusion •  MR spectroscopy Embryologic Development • Inner portion of adrenal gland = medulla •  Derived from neural crest •  Outer portion of adrenal gland = cortex •  Derived from mesothelium Anatomy •  Each adrenal gland composed of body and medial and lateral limbs •  Glands are located superior, anterior, and medial to the kidneys •  Right adrenal gland •  Relatively pyramidal in shape, V or Y shaped •  Located lateral to right diaphragmatic crus •  Situated posterior to IVC •  Left adrenal gland •  Comparatively crescentic in shape, V or Y shaped •  Located lateral to left diaphragmatic crus •  Situated posterior to pancreas & stomach Normal MRI Appearance Normal Variants • Pancake: Flattened appearance, often associated with ectopic kidney or renal agenesis • Horseshoe: Congenital fusion of the adrenal glands at the midline, often associated with other anomalies of the kidney and CNS • Adrenofusion with liver: Adhered appearance of liver and right adrenal gland Lipid nội bào? Adenoma Mỡ đại thể? Myelolipoma Xuất huyết? Sau chấn thương, tổn thương xh Nang? Nang đơn giản, giả nang, lymphangioma Mạch máu? Pheo, met Duy trì hình dáng tuyến TT bình thường? Tăng sản • • Variable appearance (“chameleon tumors”) • • Can be solid, solid and cystic, or purely cystic • • Additional work-up • • Metabolic (elevated serum and urinary metanephrines) • • 123-I metaiodobenzylguanidine (MIBG) • Bilateral • Extra-adrenal • Occur in children • Malignant 10% UNCOMMON ADRENAL MASSES:A BENIGN • MYELOLIPOMA • • GANGLIONEUROMA Adrenal Myelolipoma • Myelolipoma is an uncommon, benign, metabolically inactive tumor that is typically unilateral, accounting for 7-15% of incidental adrenal masses It is usually seen in the older population with no sex predilection Histologically, the lesion iscomposed of adipose and proliferating hematopoietic tissue with foci of hemorrhage and calcification commonly seen Spontaneous hemorrhage can rarely be significant enough to cause hypovolemic shock • On MR, fat suppressed images are helpful and demonstrate signal loss within the mass On the other hand, chemical shift imaging is not useful in diagnosis as the fat in a myelolipoma is extracellular • Ganglioneuroma is a benign neurogenic neoplasm of sympathetic ganglia that commonly manifests as an asymptomatic mass on routine imaging It is typically un-encapsulated, sharply marginated, firm and gray-white in appearance The adrenal gland is the third most common location after posterior mediastinum and the retroperitoneum Clinically, urinary catecholamines and their metabolites may be elevated On CT, ganglioneuromas appear homogeneously hypodense with slight to moderate enhancement On MR, they demonstrate low signal intensity on T1-WI and high signal intensity on T2-WI Enhancement on MR is variable, ranging from mild to marked with early enhancement being atypical UNCOMMON ADRENAL MASSES:A MALIGNANT • ADRENOCORTICAL CARCINOMA • • RARE ADRENOCORTICAL ONCOCYTIC TUMOR • • COLLISION TUMOR • • NEUROBLASTOMA IN ADULTS • • PRIMARY LYMPHOMA • • LYMPHOMA PRESENTING AS PSEUDOCYST • • SARCOMA • Adrenocortical carcinomas are rare, highly malignant neoplasm of the adrenal cortex, accounting for 0.05-0.2% of all cancers in USA They are typically large, solid and unilateral Functioning tumors usually present at cm and non-functioning tumors typically present at 10 cm Clinical syndromes with functioning tumors include Cushing syndrome (30-40%) and virilization in females (23-30%) amongst others • On NECT they appear heterogeneous owing to necrosis and enhance inhomogeneously on contrast administration The most common metastatic sites are lung, liver, nodes and bone Invasion of renal vein and IVC occurs early on with most patients presenting at stage III or IV Adrenocortical oncocytic tumor • Oncocytic tumors of the adrenal gland are rare neoplasms that originate from the adrenal cortex and are histologically, composed of epithelial cells with abundant mitochondria in their cytoplasm and no lipid deposition These tumors tend to be female predominant with a wide age range Most are hormonally inactive and are incidentally discovered on imaging They can range from 3-22 cm in size, with the malignant ones being larger in size at presentation and causing significant mass effect • Both benign and malignant tumors tend to have T1 and T2 WI MR intensities similar to the spleen Like adrenocortical carcinomas there is a slight left sided predominance, however, preservation of the capsule and lack of local invasion even in large tumors can be considered features that differentiate adrenal oncocytic tumor from adrenal cortical carcinoma Collision Tumor • Adrenal Collision tumors (ACTs) are tumors with two histologically distinct pathological entities coexisting in the adrenal gland with no admixture at interface These could be two benign tumors, two malignant tumors, or a benign tumor in contiguity with a malignant tumor for example adenoma with myelolipoma, myelolipoma with adrenocortical carcinoma or an adenoma with metastasis The most common ACT reported in literature is an adenoma with a myelolipoma However, the most problematic is an ACT composed of adenoma and metastasis in terms of diagnosis and management • Cross sectional imaging modalities like CT and MRI can play a paramount role in reliably depicting the different tumoral component in each entity thereby, guiding the appropriate management • Neuroblastoma is primarily a childhood malignancy with only 10% of cases occurring after the age of 10 In adults(> 18 years ) they have an incidence of case per million /year as compared to case per 100,000/ year in children Fundamentally, these tumors arise from primitive sympathetic neural cells in the adrenal medulla They can however arise from anywhere in the sympathetic nervous system at a paraspinal location, in the retroperitoneum or chest Metastasis occurs to regional lymph nodes, liver, skin, brain, and bone • Growing evidence suggests that adult neuroblastoma may have distinct biologic features, including low incidence of MYCN amplification, urine catecholamine elevation, and MIBG avidity Adult patients have been reported to have a higher incidence of unfavorable histologies and up to 1/3 of patients present with metastatic disease with an overall survival of 36% at years as compared to 85% for infants • Primary adrenal lymphoma (PAL) is very rare, with fewer than 200 cases reported in literature It has a tendency to affect elderly males and presents with local pain or systemic symptoms such as fever, weight loss or adrenal insufficiency In 70% of cases it is bilateral Tumors generally tend to be large with a median size of cm On CT, they may appear homogeneous /heterogeneous, hypodense /hyperdense with slight to moderate enhancement On MR, they maybe iso/hypointense on T1-WI and hyperintense on T2-WI Most demonstrate a restricted diffusion pattern with high signal intensity on diffusion weighted images (DWI), owing to their typical high cellularity • PAL is generally not a hypervascular tumor but is highly metabolically active showing increased glucose uptake on PET Typical imaging findings can possibly point to the diagnosis, however, definitive diagnosis is only established upon tissue biopsy Cystic adrenal lymphoma • In the 1990’s and earlier, case reports of primary adrenal lymphomas with cystic changes were being more frequently reported in the literature This gave rise to the assumption that primary adrenal lymphomas were complex cystic masses and secondary adrenal involvement by lymphoma presented as a well-defined, relatively homogenous soft tissue mass However , more recently several studies have shown variable results Studies have reported an equal incidence of homogeneous and heterogeneous appearing primary adrenal lymphomas, debunking this theorem Cystic adrenal lymphomas like their non-cystic counterparts are primarily non-Hodgkins B-cell lymphomas and essentially demonstrate the same clinical and biochemical characteristics Adrenal sarcoma • Primary leiomyosarcoma of the adrenal gland is a very rare malignant tumor with only 30 cases reported in literature to date Primary adrenal leiomyosarcomas are thought to originate from the smooth muscle wall of the central adrenal vein and its branches They are usually seen in elderly patients with no sex predilection They tend to be large tumors and occur in the right and left adrenal gland with equal frequency • Their imaging characteristics are indistinguishable from those of adrenocortical carcinomas and metastatic cancers Invasive disease holds an extremely poor prognosis and is suggested in the presence of venous thrombosis, adjacent organ invasion, and distant metastasis • Splenules are congenital nodules of normal splenic tissue, that fail to fuse following embryogenesis They tend to be well-circumscribed, round or ovoid and a few centimeters in diameter On CT, they demonstrate the same density and enhancement pattern as the spleen, although smaller (< cm) splenules may appear hypodense as compared to the spleen An alternative diagnosis should be entertained if the enhancement pattern differs from the spleen In addition, to being great mimickers of adrenal masses, they have been shown to mimic peritoneal metastasis, lymph node enlargement, pancreatic neuroendocrine tumors, pancreatic tail masses or metastasis and renal tumor recurrence post-nephrectomy If need arises in rare instance, a Tc99m sulphur colloid scan can be carried out to demonstrate increased uptake, provided the splenunculus is >/= to cm in diameter • Collateral vessels/varices are dilated venous vessels that serve as alternate blood circulation pathway in cases of blocked or interrupted venous flow In cases of portal hypertension there is reversal of flow in the portal vein secondary to high portal venous pressure (>12 mm Hg) The blood is redirected through perisplenic collateral vessels that appear dilated and tortuous In such instances, due to their close proximity to the adrenal gland, specifically the left adrenal gland, these may mimic a well-defined rounded/oval adrenal mass on noncontrast CT A contrast enhanced CT become imperative in the diagnosis demonstrating homogeneous enhancement similar in attenuation to the intravenous contrast enhanced blood CONCLUSION • Imaging plays an essential role in the identification, localization and characterization of adrenal masses • Some imaging features are characteristic, while other features help narrow down the differential • Take home points: •  A CT density of 60% and relative washout of >40% is diagnostic • of adenoma •  Like hemorrhage anywhere else in the body, MR signal characteristics of adrenal hemorrhage vary • with time •  Myelolipoma is a non-functioning tumors containing extracellular fat which demonstrates signal • drop on fat suppression sequences only •  A clinical history of hypertension along with a high T2 signal and positive MIBG scans are highly • suggestive of pheochromocytomas •  A malignant adrenal mass is most frequently due to a metastatic tumor with lung being the most common • primary ... hemorrhage can be unilateral or bilateral, resulting from a variety of traumatic and non-traumatic causes Non-traumatic causes can be grouped into five categories including: Stress (surgery, burns, sepsis),... solid and unilateral Functioning tumors usually present at cm and non-functioning tumors typically present at 10 cm Clinical syndromes with functioning tumors include Cushing syndrome (30-40%)... idiopathic disease Trauma typically produces unilateral, right-sided hemorrhage and is frequently associated with injuries of higher severity • Unilateral hemorrhage usually goes unnoticed while bilateral