Neurologic, endocrinologic, and pathologic findings associated with large pituitary tumors in dogs: eight cases (1976-1984).

Invasive tumors of the pituitary gland were diagnosed in 8 dogs. Seven of the dogs had been treated for pituitary-dependent hyperadrenocorticism before the onset of neurologic signs. All 8 dogs had behavior abnormalities and similar neurologic signs: 6 dogs had rotary nystagmus and 7 dogs had symmetric tetraparesis. Once neurologic signs developed, the clinical course in all 8 dogs had a mean duration of 4.7 +/- 2.0 months before death or euthanasia; 5 dogs had a clinical course of less than or equal to 2 months. Necropsy was performed in 7 dogs. The histologic diagnosis was malignant pituitary adenocarcinoma in 2 dogs and pituitary adenoma in 5 dogs.