Adrenal incidentalomas are masses of the adrenal gland discovered inadvertently during diagnostic procedures, from which a significant percentage are pheochromocytomas and these tumors are rare. Here we report a case of a 15-year-old male dog whose main complaints were a soft cervical mass and mild generalized weakness. Blood cell count, routine biochemistry, arterial blood pressure and electrocardiogram were performed. Diagnostic imaging revealed a 3.5 cm mass next to the right adrenal gland. Surgery was performed and histopathology examination of the mass confirmed a malignant pheochromocytoma. The dog died 96 hours later after surgery. At necropsy, metastasis was found in cervical lymph node. Considering vague and episodic clinical signs, pheochromocytoma antemortem diagnosis is uncommon. The main aim of this case is to highlight this endocrinology disorder, increasing the awareness of clinicians to this difficult diagnostic condition.

Key words: Dog, Incidentaloma, Pheochromocytoma