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

Marit F Van Den Berg,Luc Duchateau,Sylvie Daminet,Stephanie Scheemaeker,Kathelijne Peremans,Emmelie Stock,Sara Galac,Miguel Campos,Eva Vandermeulen,Hans S Kooistra

doi:10.1111/jvim.15908

Abstract

BackgroundInformation 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/ObjectivesTo describe planar and SPECT imaging findings in dogs with thyroid tumors, and to compare SPECT and thoracic radiography for metastasis detection.AnimalsSixty‐eight dogs with thyroid neoplasia.MethodsRetrospective study, search of medical records for dogs with thyroid neoplasia (2008‐2018).ResultsThyroid 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 ImportanceSPECT imaging is a viable imaging technique to screen for thoracic metastasis and wider use of SPECT imaging is recommended in dogs with thyroid neoplasia.

Highlights

Thyroid tumors are among the most common endocrine tumors in dogs.[1]
Importance: single-photon emission computed tomography (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
Analyzed variables consisted of tumor scintigraphic uptake, tumor scintigraphic uptake pattern, tumor scintigraphic margins, hormone status, and tumor type

Summary

| INTRODUCTION

Thyroid tumors are among the most common endocrine tumors in dogs.[1]. The vast majority of thyroid tumors in dogs are malignant, and 16% to 60% of dogs have evidence of metastases at the time of diagnosis.[1,2,3] Thyroid tumors can arise from follicular cells or from parafollicular C-cells.[2]. Single-photon emission computed tomography (SPECT) has higher sensitivity and better contrast resolution than planar imaging, and can obtain cross-sectional scintigraphic images, improving the detection of metastases.[4,16,17,19] The use of SPECT integrated with CT (SPECT/ CT) systems provides an incremental value in staging and clinical management of humans with thyroid neoplasia because it provides more correct anatomic localization and characterization of abnormal foci of radioiodine uptake.[16,17,18,20] to the authors' knowledge, this technique has not been described in veterinary medicine. The aim of this retrospective study was to describe planar and SPECT imaging findings in dogs with thyroid neoplasia, and to compare SPECT with thoracic radiography for detection of thoracic metastases

| MATERIALS AND METHODS

| RESULTS

Multiple masses with variable margins

| DISCUSSION