IMAGING AND PATHOLOGICAL FEATURES OF MYELOLIPOMA

Myelolipoma is a benign tumor consisting of mature fat interspersed wi th hematopoietic elements resembling bone marrow. Imaging findings in a large series of pathologically proved cases of myelolipoma were corr elated with the pathologic and histologic features of the lesions. Mye lolipoma manifests in four distinct clinicopathologic patterns: isolat ed adrenal myelolipoma, adrenal myelolipoma with hemorrhage, extraadre nal myelolipoma, and myelolipoma associated with other adrenal disease . Myelolipoma is difficult or impossible to detect at plain radiograph y unless the lesion is large and predominantly fatty. At ultrasound, m yelolipoma often has heterogeneous echogenicity due to its typically n onuniform architecture. Computed tomography (CT) frequently demonstrat es large amounts of fat with areas of interspersed higher-attenuation tissue. At magnetic resonance imaging, predominantly fatty areas usual ly have increased signal intensity on T1-weighted images and moderate hyperintensity complicated by the presence of marrowlike elements in t he corresponding regions on T2-weighted images, The imaging appearance of myelolipoma is altered by the presence of hemorrhage. In such case s, CT is the most accurate method for evaluation. Knowledge of the ima ging characteristics of myelolipoma usually allows presumptive diagnos is, although percutaneous needle biopsy may be needed to confirm the d iagnosis in cases of extraadrenal myelolipoma. Surgical excision is un necessary unless the diagnosis is unclear or the lesion is symptomatic . Asymptomatic, nonhemorrhagic myelolipomas do not require therapy.