Case Report: Cytologic Description of Somatotroph Pituitary Adenoma in a Cat

Abstract

This case report describes for the first time the cytologic characteristics of a hormonally secreting pituitary adenoma in a cat. An 8-year-old female spayed domestic long-haired cat was referred with a previous diagnosis of hypersomatotropism and secondary diabetes mellitus 7 months prior. Clinical signs included weight loss, polyphagia, polyuria, and polydipsia. Serum insulin-like growth factor-1 was 340 nmol/L (RI: 12-92), and CT scan revealed a hypophyseal mass, and a presumptive diagnosis of acromegaly was made. A transsphenoidal hypophysectomy was performed. A fragment of the pituitary gland was subjected to a squash preparation and cytology revealed a neuroendocrine neoplasm characterized by anisokaryosis and prominent nucleoli. Additional cytologic findings included cell cohesiveness, indistinct cytoplasmic borders, nuclear crowding, molding, and fragmentation. A diagnosis of adenoma was based on a lack of histopathologic or imaging evidence of invasion. A week later, during post-surgical hospitalization, the patient worsened and died. Histopathology from a necropsy procedure revealed fibrinosuppurative meningitis as a post-surgical complication. Pituitary adenomas might have an aggressive cytologic appearance, despite a lack of histopathologic invasion or dissemination.

Cytologic features of canine melanotroph and corticotroph pituitary adenomas

“…7,[18][19][20] Pituitary neoplasms typically exhibit distinct cytologic features commonly associated with neuroendocrine tumors, including naked or free nuclei within pale cytoplasm lacking distinct borders. 11,12 However, other neoplasms or alterations described in the sellar or suprasellar regions differ significantly from those observed in pituitary adenomas within the scope of this study.…”

“…Subsequent histologic examination confirmed the presence of an invasive pituitary macroadenoma. Cytologic findings from an imprint preparation of a feline hypophysectomy specimen 11 included hypercellularity, a background containing diffuse and amorphous pale eosinophilic material, many naked nuclei, and sheets and clusters of intact cells with indistinct borders, and increased N:C ratios. Although similar cytologic features were found in this study, the reported feline case was a somatotroph adenoma based on histopathology and IHC.…”

“…Cytology does not distinguish among the types of pituitary adenoma, but is still a valuable diagnostic tool 1 to differentiate adenomas from other types of sellar masses such as lymphoma, meningioma, craniopharyngiomas, germ cell tumor, metastatic neoplasms, hypophysitis, and degeneration, both in human and veterinary medicine 7,18–20 . Pituitary neoplasms typically exhibit distinct cytologic features commonly associated with neuroendocrine tumors, including naked or free nuclei within pale cytoplasm lacking distinct borders 11,12 . However, other neoplasms or alterations described in the sellar or suprasellar regions differ significantly from those observed in pituitary adenomas within the scope of this study.…”

“…7 While previous studies provided insights into the histologic and immunohistochemical features of canine and feline pituitary adenomas, 8-10 detailed cytologic descriptions have been reported infrequently in the veterinary literature. 11,12 Hypophysectomy is becoming a more available treatment option and also enables a definitive diagnosis via histopathology and immunohistochemistry (IHC) and allows a more rapid preliminary diagnosis via cytologic evaluation. 8,[13][14][15][16][17] The aim of this study was to describe the cytologic features of pituitary adenomas in 12 dogs that underwent hypophysectomy.…”