Biodistribution and image characteristics of 124 I-positron emission tomography in dogs with neuroendocrine neoplasia.

Radioactive iodine is frequently used for staging of human thyroid carcinomas. Iodine-124 scans performed using position emission tomography (PET) allow for more precise dosimetry of therapeutic radioiodine. The distribution of I-124 has not previously been described in veterinary medicine. The purpose of this prospective, exporatory, descriptive study is to evaluate the whole-body distribution of I-124 in dogs with suspected thyroid carcinoma. Ten dogs with either a cytologic diagnosis of a neuroendocrine neoplasm or biochemical hyperthyroidism were enrolled in a prospective clinical study. Whole-body I-124 PET/CT scans were performed and were evaluated for physiologic and pathologic uptake of I-124. The maximum and mean standardized uptake values (SUVmean) were recorded for several normal and abnormal tissues. Varying degrees of uptake were found in thyroid tumors (SUVmean = 66.37), ectopic thyroid masses (21.44), presumed metastatic lesions in lymph nodes (32.14), and the pulmonary parenchyma (4.50). In most dogs, physiologic uptake above background, measured in maximum SUV, was identified in parotid and mandibular salivary glands (14.00 and 1.57) the urinary tract (1.83), the gastrointestinal tract (19.90 stomach, 6.15 colon), the liver (1.41), and the heart (1.88). Occasionally, uptake was identified in the nasolacrimal duct (3.42), salivary duct (2.73), gallbladder (2.68), and anal gland (2.22). Physiologic uptake was also identified in normal thyroid glands and ectopic thyroid tissue. This study provides a baseline of pathologic and physiologic uptake of I-124 in dogs with thyroid carcinoma, to guide interpretation of future studies.

131 treatment in dogs with hyperthyroidism caused by a non-resectable ectopic thyroid tumour: 5 cases (2008-2019).

OBJECTIVES: This study aimed to describe the clinical and diagnostic characteristics, as well as outcomes of radioiodine treatment in dogs with hyperthyroidism caused by a non-resectable ectopic thyroid tumour. MATERIALS AND METHODS: This retrospective study reviewed the medical records between 2008 and 2018 of dogs diagnosed with hyperthyroidism secondary to a non-resectable ectopic thyroid tumour and treated with radioiodine. RESULTS: Five dogs were included in the study. Three dogs had sublingual ectopic tumours, of which one also had a unilateral cervical thyroid tumour. The remaining two dogs were diagnosed with an ectopic thyroid tumour at the level of the caudal pharynx and the heart base, respectively. All cases were treated with radioiodine. The size of the ectopic masses decreased after radioiodine treatment. Total thyroxine concentrations returned to reference ranges in all dogs. Further, clinical signs of hyperthyroidism disappeared after treatment in all patients. One dog developed myelosuppression secondary to radioiodine treatment. The dog with metastasis had a very short survival compared to the four dogs without metastasis (3 months compared to 7, 36, 50 and 24 months, respectively) and succumbed most likely to thyroid-related problems. In the remaining four dogs, their quality of life improved. They died due to diseases unrelated to the ectopic thyroid tumour. CLINICAL SIGNIFICANCE: Radioiodine therapy should be considered as a treatment option in dogs diagnosed with hyperthyroidism due to a non-resectable ectopic thyroid tumour.

Thyroid scintigraphy findings in 2096 cats with hyperthyroidism.

Thyroid scintigraphy is currently the reference standard for diagnosing and staging cats with hyperthyroidism, but few studies describing the scintigraphic characteristics in a large number of cats have been reported. The objective of this study was to better characterize thyroid scintigraphy findings by evaluating 2096 consecutive cats with hyperthyroidism that were referred over a 3.5-year period. Of these cats, 2068 (98.7%) had a high thyroid-to-salivary ratio (>1.5), whereas 2014 (96.1%) were found to have a high thyroid-to-background ratio (>6.1). When the patterns of the cats' thyroid disease were recorded, 665 (31.7%) had unilateral disease, 1060 (50.6%) had bilateral-asymmetric disease (two thyroid lobes unequal in size), 257 (12.3%) had bilateral-symmetric disease (both lobes similar in size), and 81 (3.9%) had multifocal disease (≥3 areas of increased radionuclide uptake). The number of areas of (99m) TcO(-) 4 uptake in the 2096 cats ranged from 1 to 6 (median, 2), located in the cervical area in 2057 (98.1%), thoracic inlet in 282 (13.5%), and in the thoracic cavity in 115 (5.5%). Ectopic thyroid tissue (e.g. lingual or mediastinal) was diagnosed in 81 (3.9%) cats, whereas thyroid carcinoma was suspected in 35 (1.7%) of the cats. The results of this study support conclusions that most hyperthyroid cats have unilateral or bilateral thyroid nodules, but that multifocal disease will develop in a few cats that have ectopic thyroid disease or thyroid carcinoma. Both ectopic thyroid disease and thyroid carcinoma are relatively uncommon in hyperthyroid cats, with a respective prevalence of ∼4% and ∼2% in this study.

Clinical features and treatment outcomes of 41 dogs with sublingual ectopic thyroid neoplasia.

BACKGROUND: Thyroid neoplasia is common in dogs, but there are few reports of dogs with ectopic, sublingual thyroid tumors. OBJECTIVES: To describe clinical features and outcomes of dogs with ectopic, sublingual thyroid neoplasia. ANIMALS: Five hundred and forty-four dogs with thyroid neoplasia. METHODS: This retrospective study reviewed the medical records of dogs referred for thyroid neoplasia between 1995 and 2013. Data extracted included signalment, extent of thyroid disease (eutopic or ectopic; metastasis), serum thyroxine (T4) concentration, treatment, and survival. RESULTS: Of 544 dogs with thyroid neoplasia, 41 (7.5%) dogs had ectopic sublingual thyroid tumors. The clinical features of these 41 dogs were similar to the cohort group of 503 dogs with eutopic or ectopic mediastinal thyroid tumors, but dogs with sublingual tumors were younger and less likely to have metastatic disease (15% versus 30%, P < .05). Of the 41 dogs, 28 received treatment: 21 with surgery (which included partial hyoidectomy in 13), 7 with radioiodine alone, and 13 with surgery followed by administration of radioiodine. Overall median survival was 562 days (range, 1-1,850 days). CONCLUSIONS AND CLINICAL IMPORTANCE: When compared with eutopic thyroid carcinomas, ectopic sublingual thyroid tumors generally have a less aggressive biologic behavior. Many dogs have prolonged survival, even without treatment, although death because of local tumor invasiveness or metastasis can develop in some dogs. Surgical thyroidectomy, including partial hyoidectomy, is generally effective for control of local disease. Administration of radioiodine, alone or in combination with surgical treatment, is recommended for multifocal disease or metastasis.

Partial resection of the hyoid apparatus during surgical treatment of ectopic thyroid carcinomas in dogs: 5 cases (2011-2013).

OBJECTIVE: To assess perioperative findings and postoperative complications and outcomes in dogs that had ectopic thyroid carcinomas with invasion into the hyoid apparatus and underwent tumor excision with partial hyoidectomy. DESIGN: Retrospective case series. ANIMALS: 5 client-owned dogs. PROCEDURES: Medical records of dogs that had an ectopic neuroendocrine tumor with invasion into the hyoid apparatus and underwent tumor excision with partial hyoidectomy were reviewed for information regarding perioperative and postoperative findings and outcome. During surgery in each case, the thyrohyoid and ceratohyoid or epihyoid bones (depending on degree of hyoid apparatus involvement) were sharply transected, allowing en bloc removal of the tumor. The ipsilateral cut ends of the thyrohyoid and ceratohyoid or epihyoid bones (depending on which was cut) were sutured together with polypropylene suture in a simple interrupted pattern. RESULTS: All partial hyoidectomy procedures were completed without surgical or anesthetic complications. All 5 dogs were able to eat and drink between 7 and 24 hours after surgery, with no signs of dysphagia, ptyalism, or abnormal tongue carriage. Follow-up information was obtained over a period of 173 to 587 days after surgery for all 5 dogs; 4 dogs were still alive at last follow-up. One dog was euthanized 587 days after surgery because of lethargy, inappetence, and hypercalcemia. CONCLUSIONS AND CLINICAL RELEVANCE: From this limited series of cases, results suggested that partial resection of the hyoid apparatus during removal of ectopic thyroid carcinoma may be tolerated well and be associated with very good functional outcomes in dogs.

Ectopic thyroid carcinoma infiltrating the right atrium of the heart in a dog.

A 12-year-old intact female shih tzu dog was diagnosed with an ectopic thyroid carcinoma infiltrating the right atrium of the heart. Echocardiography and computed tomography were helpful in diagnosis; a definitive diagnosis was made based on postmortem histopathology and immunohistochemistry. The patient lived 428 days beyond diagnosis with only medical management.

Ectopic thyroid in the aortic valve of a Han Wistar rat.

Histological examination of the heart of a clinically normal, 10-week-old female Han Wistar rat revealed a 600 x 400-mum mass of ectopic thyroid tissue within the subendothelial connective tissue of the aortic valve. The mass protruded into the left ventricular lumen and was composed of single layers of cuboidal to low-columnar epithelium organized into follicles often containing colloid. Parafollicular cells were not evident. To the authors' knowledge, this is the first report of intracardiac ectopic thyroid gland in the rat and the first report of ectopic thyroid within a heart valve in a mammal.