Symptomatic Intraspinal Oncocytic Adrenocortical Adenoma

Most intraspinal neoplasms of epithelial origin are metastases from primary carcinomas. Benign epithelial tumors are rarely found at this site. We here present the case of a 44-year-old woman with a lesion in the cauda equina that fulfilled the radiologic criteria of schwannoma and caused clinical symptoms for 3 years. The excised tumor was composed of nests of large polygonal cells with eosinophilic partial granular cytoplasm. Significant atypia, necrosis, and mitosis were absent from this lesion. The tumor showed diffuse positivity for melan-A, synaptophysin, and alpha-inhibin. Steroidogenic factor 1 and cytokeratins 8 and 18 were focally seen in the absence of S-100 and chromogranin. This immunoprofile indicated adrenocortical origin. Ultrastructural examination showed abundant mitochondria, suggesting an oncocytic tumor. The diagnosis of an oncocytic adrenal cortical adenoma was made. These extraadrenal tumors are thought to arise from heterotopic adrenocortical tissue in the spinal cavity. Oncocytic tumors are rare neoplasms and they comprise non-functioning variants of adrenal cortical adenomas. To date, only five such intraspinal tumors have been observed. Immunohistochemistry excluded oncocytic paraganglioma, oncocytic meningioma, renal cell carcinoma, alveolar soft part sarcoma, and granular cell tumor. A view of the literature of these rare but probably underdiagnosed intraspinal tumors is given.