Background: Ectopic Cushing's syndrome (ECS) associated with malignant tumors, such as small cell lung carcinoma, bronchial carcinoids, and pheochromocytoma, has been reported in human medicine. However, ECS related to pheochromocytoma has not been reported in dogs.
Case presentation: An 11-year-old castrated, male Scottish terrier was diagnosed with a left adrenal mass. Cushing's syndrome was suspected based on clinical signs, including pot belly, polyuria, polydipsia, bilateral alopecia, recurrent pyoderma, and calcinosis cutis. Cushing's syndrome was diagnosed on the basis of consistent clinical signs and repeated adrenocorticotropic hormone (ACTH) stimulation tests. In addition, tests for fractionated plasma metanephrine/normetanephrine suggested a pheochromocytoma. Unilateral adrenalectomy was performed after medical management with trilostane and phenoxybenzamine. Histopathology confirmed a diagnosis of pheochromocytoma without cortical lesions. After surgery, fractionated metanephrine/normetanephrine and the findings of low-dose dexamethasone suppression and ACTH stimulation tests were within the normal ranges without any medication. There were no clinical signs or evidence of recurrence and metastasis on thoracic and abdominal X-rays and ultrasonography up to 8 months after surgery.
Conclusions: Pheochromocytoma should be considered a differential diagnosis for dogs with Cushing's syndrome with an adrenal tumor. A good prognosis can be expected with prompt diagnosis and surgical intervention.
Keywords: Adrenal tumor; Dog; Ectopic Cushing’s syndrome; Hyperadrenocorticism; Pheochromocytoma.