Incidental and Nonincidental Canine Thyroid Tumors Assessed by Multidetector Row Computed Tomography: A Single‐centre Cross Sectional Study in 4520 Dogs

Abstract

Thyroid nodules are common in dogs and are increasingly likely to be detected with the increased use of advanced imaging modalities. An unsuspected, nonpalpable, asymptomatic lesion, defined as a thyroid incidentaloma, may be discovered on an imaging study unrelated to the thyroid gland. The objective of this single-center cross-sectional study was to assess the prevalence and computed tomography (CT) characteristics of incidental and nonincidental thyroid tumors in a large population of dogs, using prospective recruitment of patients undergoing CT examination for various reasons during the period of 2005-2015. Unilateral or bilateral thyroid masses were detected in 96/4520 dogs (prevalence, 2.12%; 95% confidence interval [CI], 1.70-2.54%). Seventy-nine (82.3%) lesions were malignant and 17 (17.7%) were benign. Masses were discovered incidentally in 34/96 dogs (overall prevalence of incidentaloma, 0.76%; 95% CI, 0.51-1.02), and 24 (70.6%) of these 34 masses were thyroid carcinomas. Among the CT variables assessed, mineralization, vascular invasion, and tissue invasion were detected only in malignant tumors. Intratumoral vascularization was significantly associated with the presence of thyroid malignancy (P < 0.001). Although incidental thyroid nodules in dogs are relatively rare, they are often malignant. Findings indicated that the neck should be thoroughly assessed in middle-aged and old patients undergoing body CT for various reasons. Thyroid nodules detected incidentally on CT should be sampled to avoid missing thyroid cancer.

Computed Tomography in Veterinary Medicine: Currently Published and Tomorrow's Vision

“…In the case of canine thyroid tumours, CT is recommended for both preoperative diagnosis and for staging [52,53]. It has also been recommended that any middle aged dog that has a body CT should be checked for incidental thyroid nodules as, although rare, they are identifiable [54]. CT is already regularly used for staging cancers, and each tumour type must be individually assessed as to which method is most appropriate for this vital process.…”

Non-functional thyroid cystadenoma in three boxer dogs

“…Thyroid tumours account for 1.1 to 3.8% of all neoplasms and approximately 10–15% of all head neoplasms in dogs [1–5]. In some studies, boxers, beagles, golden retrievers and Siberian huskies were more commonly affected compared to other breeds [2, 4–8].…”

“…In some studies, boxers, beagles, golden retrievers and Siberian huskies were more commonly affected compared to other breeds [2, 4–8]. However, another recent study found no association between breed and development of thyroid neoplasia [1]. Thyroid carcinomas are more frequently diagnosed antemortem than thyroid adenomas [1, 4–6, 15], which are often discovered serendipitously during physical examination or at necropsy [5, 8].…”

“…However, another recent study found no association between breed and development of thyroid neoplasia [1]. Thyroid carcinomas are more frequently diagnosed antemortem than thyroid adenomas [1, 4–6, 15], which are often discovered serendipitously during physical examination or at necropsy [5, 8]. Dogs with thyroid carcinomas have evidence of metastasis at the time of diagnosis in from 16 to approximately 60% of case [11, 14, 16].…”

“…Cysts can also be observed with malignant thyroid tumours, namely papillary thyroid carcinomas, which are rarely reported in dogs [15, 17]. Although cystadenomas are occasionally mentioned in large case series of thyroid neoplasia in dogs, or as incidental post-mortem findings, detailed clinical features of these cases have not been described [1, 5, 7, 18]. Two individual case reports described thyroid cystadenoma with concurrent hyperthyroidism in a German shepherd dog and an English springer spaniel [19, 20].…”