Metastatic Alveolar Soft Part Sarcoma Presenting as an Adrenal Incidentaloma: A Case Report with Review of Literature.

Background. Metastasis of alveolar soft part sarcoma (ASPS) to the adrenal gland is infrequent, with only eight patients reported in the literature. Here we present an ASPS in an adolescent girl presented as a hypervascular adrenal incidentaloma along with a review of the available literature. This study aims to serve as a reference to aid in the pre-operative radiological and histopathological diagnosis of this rare entity. Case presentation. A 17-year-old adolescent girl presented to the Department of Urology after the detection of a hypervascular left adrenal incidentaloma on follow-up PET-CT, five months post-surgery for frontal bone ASPS. The radiological differential diagnoses were adrenocortical carcinoma, pheochromocytoma, and metastatic ASPS. The post-operative adrenalectomy specimen, on gross examination, revealed a solid, variegated tumor replacing the entire normal adrenal parenchyma. Haematoxylin and eosin-stained sections showed a tumor with cells dispersed in nests separated by large fibrovascular septae. The tumor cells were large, polygonal with abundant clear to eosinophilic cytoplasm and prominent nucleoli. Occasional mitotic figures, foci of necrosis, dystrophic calcification, and sinusoidal and vascular invasion were noted. Histopathological differential diagnoses were metastatic ASPS, a primary adrenocortical carcinoma, and local infiltration/metastases from renal cell carcinoma. Ancillary studies including immunohistochemistry, fluorescent in situ hybridization (FISH), and ultrastructural examination helped to confirm the diagnosis of alveolar soft part sarcoma metastatic to the adrenal gland. Conclusion. ASPS presenting as a hypervascular incidentaloma is rare and is likely to be misdiagnosed, especially as adrenocortical carcinoma, pheochromocytoma, and renal cell carcinoma. The differential diagnosis is further complicated by an overlap of pathological features among these entities. A relevant clinical history and ancillary tests are mandatory to diagnose these tumors. Early detection can help timely therapeutic intervention that can improve patient outcome.