Radiological concern for liposarcoma unmasked as extra-adrenal myelolipoma: A case report

Extra-adrenal myelolipomas (EAMLs) are rare, benign tumors composed of mature adipose tissue and trilineage hematopoiesis, most commonly arising in the retroperitoneum. When large or radiographically atypical, they can mimic malignant entities, such as well-differentiated liposarcomas, often necessitating tissue diagnosis. The present case report describes the case of a 79-year-old male patient with a history of pituitary adenoma treated with resection and radiation, resulting in secondary adrenal insufficiency and central hypothyroidism, who presented with progressive weakness, recurrent falls, and an unintentional weight loss of 18-20 lb. The laboratory evaluation did not reveal any notable findings, apart from known endocrine abnormalities. Non-contrast computed tomography (CT) revealed a heterogeneous, fat-containing left retroperitoneal mass, measuring 6.3x7.0x8.8 cm, with apparent ureteral encasement, concerning for liposarcoma. Surgical intervention was deferred due to comorbidities. A CT-guided biopsy demonstrated mature adipose tissue with trilineage hematopoietic elements, positive for CD45, MPO, CD71 and CD61, with flow cytometry excluding a clonal process, confirming EAML. EAMLs are exceedingly rare, with <100 cases reported, and definitive diagnosis relies on histopathology. The case described herein is notable for its association with remote Cushing's disease, supporting a potential link between chronic endocrine stimulation and EAML pathogenesis. EAML should be considered in the differential diagnosis of fat-containing retroperitoneal masses with atypical imaging features.