A Comparison of Medullary Thyroid Carcinoma and Thyroid Adenocarcinoma in Dogs: A Retrospective Study of 38 Cases

Abstract

The medical records of 38 dogs with thyroid neoplasia that were treated by surgical excision of the tumor, or had an incisional biopsy performed as a diagnostic procedure, were reviewed. Of the 38 dogs, 21 (55%) had resectable tumors, whereas 17 (45%) had an incisional biopsy as the tumors were nonresectable. All dogs had an initial diagnosis of thyroid carcinoma. The type of carcinoma was confirmed in 33 dogs by histological and immunohistochemical examination. Twelve dogs (36%) had medullary thyroid carcinoma, and 21 dogs (64%) had thyroid adenocarcinoma. Of the 12 dogs with medullary thyroid carcinoma, 10 (83%) had resectable tumors. Of the 10, three (30%) had at least a 1-year survival. None had radiographic evidence of metastasis at the time of surgery. Of the 21 dogs with thyroid adenocarcinoma, 11 (52%) had resectable tumors. Of the 11 dogs, five (45%) had at least a 1-year survival. Three dogs had radiographic evidence of metastasis at the time of surgery. Of 10 dogs with nonresectable thyroid adenocarcinoma, two dogs (20%) had at least a 1-year survival. In the dogs in this study, medullary thyroid carcinoma was more prevalent than previously reported. Most of the medullary thyroid carcinomas were well circumscribed and resectable. Medullary thyroid carcinoma may possess gross and histological characteristics of a less malignant nature when compared with other thyroid carcinomas.

Primary brain involvement of disseminated histiocytic sarcoma in a Rottweiler dog - histopathology, ¹⁸F-fluorodeoxyglucose positron emission tomography and 7 T-magnetic resonance imaging findings: a case report

“…Although medullary thyroid carcinoma accounts for 16-36% of thyroid carcinomas in dogs, the incidence of canine MMFC is unknown (Leblanc et al 1991;Carver et al 1995;Campos et al 2014). Only seven sporadic cases have been reported in dogs (Moore et al 1984;Brown et al 2001;Campos et al 2014).…”

A dog pedigree with familial medullary thyroid cancer

“…We screened individuals lll:1, lll:2, lll:3 and lll:4 for mutations in exons 12-21 of the dog Ret gene (corresponding to human exons [8][9][10][11][12][13][14][15][16][17], where all the known MEN2 and MTC related mutations are located by sequencing analysis. The screening of other exons that corresponded to other human RET exons was carried out by SSCP.…”

“…The most common thyroid tumours in dogs are of follicular origin (12). MTC is reported to correspond to 36% of the dog thyroid carcinomas and calcitonin is present in 70-100% of cases (14,15).…”

Functional Thyroid Gland Adenoma in a Dog Treated with Surgical Excision Alone

“…Most are described as carcinomas, of which less than 10% secrete thyroid hormones [2,3,5,8,10]. Benign thyroid adenomas are clinically rare, usually discovered at necropsy as incidental findings consisting of nonfunctional small nodules [3,5].…”

“…Most reported cases consist of solid large carcinomas sometimes with dyspnea, coughing, dysphonia, or hypothyroidism [2,3,7,10]. Although canine hyperthyroidism is seen only in dogs with thyroid tumors [3], it is thought to be an extremely rare disease.…”