RESUMEN
Background: Primary pituitary carcinoma is rarely reported in dogs and only few reports describe its malignancy. In veterinary literature, primary pituitary carcinomas correspond up to 2.4% to 3.4% of intracranial neoplasms found in dogs andinformation regarding its biological behavior is quite limited. In humans, primary pituitary carcinomas represent less than1.0% of all tumors found in the pituitary gland. The proposed classification for pituitary carcinoma in humans and dogsdetermines that the tumor must have its origin in adenohypophyseal region and disseminated metastasis by cerebrospinalfluid or systemically to other organs must be observed. In dogs, a few reports have described primary pituitary carcinoma.The goal of this report was to describe clinical, tomographic, histopathological and immunohistochemistry features of abitch with primary pituitary carcinoma with adjacent invasion.Case: A 7-year-old female spayed Golden Retriever dog was assessed by general practice due progressive weight loss,muscular atrophy, lethargy, blindness, head pressing, and hyporexia for 21 days. Computed tomography (CT) showeda cerebral parenchyma with expansive extra-axial base formation, originating from sella turcica topography, measuringabout 2.0 cm dorsally, displacing the third ventricle, suggesting the diagnosis of pituitary neoplasia. The hormones thyroidstimulating hormone (TSH) and total thyroxine (T4) as well as stimulation ACTH test were unremarkable. After 7 days,neurological clinical signs progressed and unfortunately the patient died ten days later after hospitalization. A necropsyexam revealed pituitary gland with increased dimensions (2.5 x 2.0 cm). Histopathological fi ndings revealed tumor proliferation in pituitary gland. The neoplasm showed invasion to the nervous parenchyma and metastatic foci between the brainlobes. Immunohistochemistry was positive for keratin and neuron-specifi c enolase...