A COMPARISON OF MEDULLARY-THYROID CARCINOMA AND THYROID ADENOCARCINOMA IN DOGS - A RETROSPECTIVE STUDY OF 38 CASES

The medical records of 38 dogs with thyroid neoplasia that were treate d by surgical excision of the tumor, or had an incisional biopsy perfo rmed 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 th yroid carcinoma. The type of carcinoma was confirmed in 33 dogs by his tological and immunohistochemical examination. Twelve dogs (36%) had m edullary thyroid carcinoma, and 21 dogs (64%) had thyroid adenocarcino ma. Of the 12 dogs with medullary thyroid carcinoma, 10 (83%) had rese ctable tumors. Of the 10, three (30%) had at least a 1-year survival. None had radiographic evidence of metastasis at the time of surgery. O f the 21 dogs with thyroid adenocarcinoma, 11 (52%) had resectable tum ors. Of the 21 dogs, five (45%) had at least a 1-year survival. Three dogs had radiographic evidence of metastasis at the time of surgery. O f 10 dogs with nonresectable thyroid adenocarcinoma, two dogs (20%) ha d at least a 1-year survival. In the dogs in this study, medullary thy roid carcinoma was more prevalent than previously reported. Most of th e medullary thyroid carcinomas were well circumscribed and resectable. Medullary thyroid carcinoma may possess gross and histological charac teristics of a less malignant nature when compared with other thyroid carcinomas. (C)Copyright 1995 by The American College of Veterinary Su rgeons