Effective treatment with mitotane for a canine case of presumed ectopic Cushing’s syndrome-related pheochromocytoma

Background: In humans, ectopic Cushing’s syndrome (ECS) is characterized by hypercortisolemia, which is caused by small lung carcinoma, bronchial carcinoids, and pheochromocytoma. In dogs, only a few cases of ECS associated with pheochromocytoma have been reported to date. Case Description: Herein, we describe a canine case of malignant pheochromocytoma that is presumed to be the cause of ECS. An 11-year-old, castrated, male Toy Poodle with hypercortisolemia was diagnosed with an adrenal tumor (AT) and treated with mitotane. Although repeated adrenocorticotropic hormone stimulation tests revealed improvement in the dog’s condition by mitotane treatment, its condition started declining 197 days post-diagnosis, and he died on day 280. The necropsy revealed the AT was a pheochromocytoma, not an adrenocortical tumor. However, because of no pathological change in the pituitary gland and the other adrenal gland, pheochromocytoma was presumed to be the cause of ECS. Conclusion: This is the first report that describes the effectiveness of mitotane against presumed ECS-related pheochromocytoma