Introduction: Oncocytomas are tumours composed by oncocytes, cells with granular and eosinophilic cytoplasm filled with mitochondria. It is a neoplasm that can arise in several organs (more commonly described in the kidney, salivary gland and thyroid). Oncocytoma arising in the adrenal gland is a rare finding. Most of them are benign and non-functioning and are detected incidentally. However, functional adrenal oncocytomas presenting as Cushings syndrome and phaeochromocytoma have been reported.
Case report: 55 years old woman with progressive weight gain in the last year. Medical history: smoker, arterial hypertension, dyslipidemia, gastroesophageal reflux disease and past infection with the hepatitis B virus. She had developed edema of her face, abdomen and ankles and had frequent headaches. Physical examination: truncal and centripetal obesity, thin extremities with muscle atrophy, plethoric moon face, echymoses and hirsutism. Blood pressure: 120/85 treated with losartan 50 mg/24 h, amiloride hydrochlorothiazide 5/50 mg/24 h and atenolol 50 mg/24 h. Laboratory evaluation: fasting blood glucose 86 mg/dl, total cholesterol 218 mg/dl, HbA1c 6.3%, TSH 0.96 μIU/ml, serum cortisol (0800 h) 22 μg/dl (525), serum cortisol (after 1 mg overnight dexamethasone suppression) 10 μg/dl, serum cortisol (after 0.5 mg dexamethasone every 6 h for 48 h suppression) 27 μg/dl, urinary free cortisol repeatedly reased (593, 388 μg/24 h), ACTH 1 pg/dl, rest adrenal hormonal profile normal. Computed tomography: 2.2 cm mass in the right adrenal gland. From these findings, the final diagnosis for this patient was Cushings syndrome and we decided laparoscopic right adrenalectomy. Histopathology: adrenal adenoma with encapsulated oncocytoma without capsular invasion. The patient is receiving glucocorticoid replacement therapy 6 months after the surgery with progressive reduction. She is waiting to see clinical and analytical evolution to suspend such treatment.
Conclusion: Adrenocortical oncocytoma, although extremely rare, should be considered in the differential diagnosis in adrenal masses. They are usually non-functional and benign but few cases are functioning tumours and may cause Cushings syndrome. To make a correct diagnosis, biochemical, clinical and histological features must be analysed together.