A Case Report of Feline Pituitary Carcinoma with Hypercortisolism

Feline pituitary tumors are rare. An 8-year-old male Japanese domestic cat presented with anorexia and emaciation. The cat died 17 days after admission from progressive neurological symptoms. At necropsy, a pituitary tumor measuring 25 × 18 × 15 mm was found. Microscopically, the tumor was divided into multiple lobules and had grown invasively into the adjacent brain tissue and sphenoid bone. Tumor cells had pleomorphic nuclei with prominent centrally located nucleoli and abundant amphophilic polygonal cytoplasm. Immunohistochemically, the tumor cells stained with anti-adrenocorticotropic hormone (ACTH), α-melanin-stimulating hormone (MSH) and β-endorphin antibodies. Ultrastructurally, the cytoplasm of the tumor cells contained various sized secretory granules. Based on these pathological findings, this tumor was diagnosed as pituitary carcinoma originated from pars intermedia cells.