Planar and single-photon emission computed tomography imaging in dogs with thyroid tumors: 68 cases

Background: Information on scintigraphy findings in dogs with thyroid neoplasia is scarce. The use of single-photon emission computed tomography (SPECT) could improve detection of metastatic disease. Hypothesis/Objectives: To describe planar and SPECT imaging findings in dogs with thyroid tumors, and to compare SPECT and thoracic radiography for metastasis detection. Animals: Sixty-eight dogs with thyroid neoplasia. Methods: Retrospective study, search of medical records for dogs with thyroid neoplasia (2008-2018). Results: Thyroid scintigraphy was available from 68 dogs, of which 6 presented after surgical resection. Radionuclide uptake was increased in 56% of dogs, decreased in 24%, and comparable to that of the salivary glands in 13%. The remainder had multiple masses with variable uptake. A homogeneous uptake pattern was present in 16% and a heterogeneous uptake pattern in 73%. In 11% (all dogs with multiple masses), various uptake patterns were present. Thyroid tumors were well delineated in 55%. There was a significant association between hormone status and uptake pattern (P =.009), with a heterogeneous uptake pattern in the majority of euthyroid dogs, and hormone status and tumor circumscription (P =.003), with well-circumscribed margins in the majority of hypothyroid and hyperthyroid dogs. Thoracic SPECT imaging was available in 39 dogs and identified metastatic lesions in 15 dogs. Thoracic radiographs were performed in 14 of these dogs, and detected metastases in 3 dogs. Conclusions and Clinical Importance: SPECT imaging is a viable imaging technique to screen for thoracic metastasis and wider use of SPECT imaging is recommended in dogs with thyroid neoplasia