Malignant adrenal rest tumor of the retroperitoneum producing adrenocortical steroids.

We present a case of a malignant adrenal rest tumor arising from the retroperitoneum with Cushing's syndrome in a 31-year-old female. Her serum cortisol and dehydroepiandrosterone sulfate levels were elevated, while adrenocorticotropic hormone levels were low. Computed tomography scans and magnetic resonance imaging revealed a retroperitoneal tumor with no visible lesions in the adrenal glands and ovaries. From those results and the histopathologic findings following biopsy of an enlarged supraclavicular lymph node, the patient was diagnosed as a malignant adrenal rest tumor of the retroperitoneum. Despite chemotherapy, the patient died of rapid development of multiple metastases. Autopsy revealed a large tumor that extended around the abdominal aorta from the levels of the left kidney to the aortic bifurcation with generalized metastases. Tumor cells were characterized by clear and eosinophilic cytoplasm and atypical nuclei that exhibited frequent and atypical mitoses. Immunohistochemistry regarding steroidogenesis was performed and revealed that the tumor cells were immunopositive for adrenal 4 binding protein/steroidogenic factor-1, cholesterol side-chain cleavage enzyme, 17α-hydroxylase, and 21-hydroxylase. We thus elucidated the adrenocortical steroid production in the tumor cells causing Cushing's syndrome. This case report first demonstrates the steroidogenic capacity in a malignant adrenal rest tumor.