Histopathologic Findings in Canine Pituitary Glands

Abstract

To optimize the histologic evaluation of hypophysectomy specimens, sections of 207 canine pituitary glands (196 postmortem, 11 hypophysectomy specimens) were reviewed. Adenohypophyseal proliferation was the most common (n = 79) lesion. Proliferative lesions were sparsely to densely granulated; the granules were usually basophilic to chromophobic and periodic acid-Schiff-positive. Adenohypophyseal proliferation was classified as hyperplasia (n = 40) if ≤2 mm diameter with intact reticulin network, as microadenoma (n = 22) for 1-5 mm homogeneous nodules with lost reticulin network, or as macroadenoma (n = 17) for larger tumors. Craniopharyngeal duct cysts were common incidental lesions and the only lesion in 15 dogs. Uncommon diagnoses included lymphoma (n = 4), hemorrhagic necrosis (n = 4), metastatic carcinoma (n = 3), hypophysitis (n = 3), ependymoma (n = 2), craniopharyngioma (n = 2), and 1 case each of metastatic melanoma, pituicytoma, gliomatosis, germ cell tumor, meningioma, and atrophy. The pituitary histologic diagnosis was associated with hyperadrenocorticism (HAC; P < .001) and adrenocortical histologic diagnosis ( P = .025). Both HAC and adrenocortical hyperplasia showed a positive trend with the degree of adenohypophyseal proliferation. The association of adrenocortical hyperplasia with HAC was not significant ( P = .077). Dogs with adenohypophyseal proliferations were older than dogs with normal pituitary glands ( P < .05). Brachycephalic breeds were overrepresented among dogs with pituitary macroadenoma or craniopharyngeal duct cysts, but the association was not statistically significant ( P = .076). Adenohypophyseal hyperplasia was more common than adenoma among postmortem specimens, but was unexpected in >80% of cases. Pituitary macroadenoma was the most common diagnosis in hypophysectomy specimens.

Immunohistochemical Evaluation of Canine Pituitary Adenomas Obtained by Transsphenoidal Hypophysectomy

“…4 This apparent difference in breed distribution could reflect differences in canine populations. The male:female ratio in the current case series was 3:1, but no reference population was available to determine whether this reflected a sex predilection for pituitary adenoma, which was not apparent in our retrospective study 16 and not reported in other studies.…”

“…At least 500 cells were counted (Count Tool in Adobe Photoshop CC 2015) in photographs taken at 400Â magnification. See the previous study 16 for details of the statistical analysis.…”

Clinical characteristics and outcome in 15 dogs treated with transsphenoidal hypophysectomy for nonfunctional sellar masses

“…Transsphenoidal surgical removal of functional pituitary tumors in dogs and cats can be performed by experienced surgeons with low morbidity and mortality 10–16 . Pituitary adenoma is the most common tumor of the pituitary fossa in dogs, but other sellar masses can occur, including meningioma, craniopharyngioma, ependymoma, germ cell tumors, and metastatic neoplasms 17–20 . NFSM become clinically significant when they cause compression of the hypothalamus and surrounding brain structures 10,18,21 .…”

“… 10 , 11 , 12 , 13 , 14 , 15 , 16 Pituitary adenoma is the most common tumor of the pituitary fossa in dogs, but other sellar masses can occur, including meningioma, craniopharyngioma, ependymoma, germ cell tumors, and metastatic neoplasms. 17 , 18 , 19 , 20 NFSM become clinically significant when they cause compression of the hypothalamus and surrounding brain structures. 10 , 18 , 21 TSH is less commonly performed for NFSM producing clinical signs due to mass effect.…”

A Recurrent Suprapituitary Ependymal Cyst Managed by Endoscopy-Assisted Transsphenoidal Surgery in a Canine: A Case Report

“…One study also described the surgical removal of an epidermoid cyst in the fourth ventricle via suboccipital craniotomy and partial first cervical laminectomy (16). Cell proliferations of the pituitary gland are common in dogs, and result in the formation of micro- or macroadenomas, adenocarcinomas, hyperplasia, craniopharyngeal duct cysts, secondary neoplasms, and hypophysitis (17). Functional disturbance of the pituitary gland, which causes canine hypercortisolism (central Cushing syndrome), is found in most cases (18, 19).…”