TC-99M-PERTECHNETATE IMAGING OF THYROID-TUMORS IN DOGS - 29 CASES (1980-1992)

Thyroid gland scintigraphy was performed in 29 dogs with histologicall y confirmed thyroid tumors. Twenty dogs were female, and 9 were male. Median age was 10 years. Of the 29 dogs, 21 were initially examined be cause of cervical swelling or a cervical mass. Of the 29 tumors, 24 we re thyroid adenocarcinomas, 1 was a C-cell carcinoma, 3 were undiffere ntiated carcinomas, and 1 was a thyroid adenoma. Serum triiodothyronin e and thyroxine concentrations were determined in 25 dogs. Sixteen dog s were euthyroid, 6 were hyperthyroid, and 3 were hypothyroid. In all 29 dogs, results of scintigraphy were abnormal. The most common scinti graphic appearance (13 dogs) was a unilateral thyroid mass with increa sed radionuclide uptake, relative to that of the parotid salivary glan ds. There did not appear to be an association between distribution of radionuclide uptake and histologic diagnosis, although there appeared to be an association between distribution of uptake and histologic deg ree of capsular invasion. All 4 dogs with extensive capsular invasion and 11 of 17 dogs with limited capsular invasion had poorly circumscri bed, heterogeneous uptake of pertechnetate by the tumor. All hyperthyr oid dogs had intense uptake, and 5 of 6 hyperthyroid dogs had well-cir cumscribed, homogenous uptake. Scintigraphy did nor appear to offer an y additional benefit, compared with thoracic radiography, for detectio n of pulmonary metastases.