A Case of Oncocytic Adrenocortical Neoplasm of Borderline (Uncertain) Malignant Potential

Oncocytic neoplasms are tumors composed predominantly or exclusively of oncocytes (large polygonal cells with granular eosinophilic cytoplasm due to abnormal mitochondrial accumulation). These tumors are frequently reported in the thyroid, kidneys, and salivary glands. However, they are distinctly rare in the adrenal cortex. Oncocytic adrenocortical neoplasms (OAN) are classified regarding their biological behavior by their histological features according to the Lin-Weiss-Bisceglia system (LWB). Here, we report a case of OAN of borderline or uncertain malignant potential (BMP) with subsequently identified papillary thyroid carcinoma (PTC). A 34-year-old female with a nine-month history of fatigue presented with chest pain. A right adrenal mass was incidentally found while ruling out pulmonary embolism. A CT-guided adrenal biopsy, although not routinely indicated, was performed and interpreted as malignant with no definitive origin. Hormonal workup was unremarkable. PET-scan showed hypermetabolic adrenal mass with peak standardized uptake value of 15, suspicious of malignancy. A hypermetabolic thyroid nodule was also identified, but there was no evidence of metastatic disease. The patient underwent adrenalectomy, and the initial pathology report was interpreted as atypical pink cell tumor. A second pathology report from another laboratory favored OAN based on the morphology and immunohistochemical staining. While the histologic criteria of malignancy were not met, the large tumor size makes it compatible with BMP according to LWB criteria. A follow-up thyroid ultrasound revealed a complex thyroid nodule. A total thyroidectomy was performed, and pathology was consistent with PTC. Of interest, PTC frequently shows an increase in mitochondrial content, which is characteristic of oncocytic tumors. This case illustrates that OAN, although rare, should be considered in the differential diagnosis of adrenal masses. When OAN is identified, it should be classified regarding its biological behavior as benign or malignant using the LWB system and, eventually, the reticulin algorithm of Duregon, et al. Oncocytoma can be confirmed ultrastructurally or by immunohistochemistry. Studying the gene mutations in patients presenting with oncocytic malignancies and other tumors that demonstrate mitochondrial proliferation as PTC might help to understand the role of mitochondrial proliferation in cancer development.