Corticotroph-producing pituirary macroadenoma and malignant pheochromocytoma in a dog: clinico-pathological findings and follow-up.

In dogs, approximately 10-20% of cases with pituitary-dependent hypercortisolism (PDH) are associated with a pituitary macroadenoma and neurological signs (Feldman and Nelson, 2004). Altered mentation (disorientation and depression), ataxia, tetraparesis, pacing, pathologic nystagmus, circling, head pressing, behavioural changes, blindness, seizures and coma have been reported in dogs with PDH due to a pituitary macroadenoma (Feldman and Nelson, 2004). Recently, a pituitary apoplexy-like disease has been reported in dogs where there is sudden development infarction and hemorrhage in a pituitary macroadenoma leading to acute neurological signs (Bertolini et al, 2007). There are few treatment options once a pituitary macroadenoma has resulted in neurological signs. Transsphenoidal hypophysectomy is an effective therapy in dogs, however, the survival and disease-free fractions after surgery decrease with increasing tumor size (Hanson et al, 2005; Hanson et al, 2007). In giant pituitary adenomas (> 1.5 cm in diameter) the aim of pituitary surgery is considered more palliative through debulking of the tumor mass effect. In those cases surgery is usually not curative for the Cushing’s disease and medical treatments remain necessary to manage the hypercortisolism. Pheochromocytoma is a tumor of the chromaffin cells of the adrenal medulla or sympathetic paraganglia (Barthez et al, 1997). A variety of vague and non-specific clinical signs attributed to excessive secretion of catecholamines has been reported in dogs with pheochromocytoma (Gilson et al, 1994; von Dehn et al, 1995; Barthez et al, 1997). Antemortem diagnosis of pheochromocytoma is difficult because of lack of specific clinical signs (Barthez et al, 1997). In a dog with hypercortisolism a giant pituitary corticotroph macroadenoma was diagnosed. After hypophysectomy the dog survived for 13 months in complete remission. The post mortem examination revealed absence of pituitary tissue and the presence of a pheochromocytoma in the right adrenal gland.