Uncommon tumor, uncertain course: functional oncocytic adrenocortical neoplasm with mild autonomous cortisol secretion.

Oncocytic adrenocortical neoplasms are rare adrenal tumors that are usually discovered incidentally. Although most are nonfunctional, about one-third secrete hormones, most often cortisol. We present the case of a 59-year-old man with a right adrenal mass and long-standing, difficult-to-control hypertension. Biochemical testing revealed a 1 mg dexamethasone suppression test (DST) of 2.8 μg/dL (77.25 nmol/L) (reference range: <1.8 μg/dL; <50 nmol/L), a repeated 1 mg DST of 2.3 μg/dL (63.44 nmol/L), a baseline adrenocorticotropic hormone of 6.5 pg/dL (1.4 pmol/L) (reference range: 7.2-63.3 pg/mL; 1.6-13.9 pmol/L), and a dehydroepiandrosterone of 66.5 μg/dL (1.80 μmol/L) (reference range: 51.7-295 μg/dL; 1.4-8.0 μmol/L); consistent with mild autonomous cortisol secretion. Adrenal computed tomography (CT) showed a stable 21 mm indeterminate adrenal nodule with an unenhanced CT attenuation of 22 Hounsfield units. The patient underwent laparoscopic adrenalectomy, and pathology confirmed an oncocytic adrenocortical neoplasm of uncertain malignant potential. Postoperatively, a 1 mg DST was within normal limits, confirming the resolution of mild autonomous cortisol secretion. He is currently under surveillance with annual CT imaging. This case underscores the need to consider oncocytic adrenocortical neoplasms in the differential diagnosis of adrenal incidentalomas and highlights the importance of further research into this rare entity.