Clinical, Pathologic, and Immunohistochemical Prognostic Factors in Dogs with Thyroid Carcinoma

Abstract

BackgroundPrognostic markers for dogs with thyroid tumors are limited.Hypothesis/ObjectivesTo identify clinical, pathologic, and immunohistochemical prognostic factors for dogs with thyroid tumors.AnimalsSeventy dogs with thyroid neoplasia.MethodsRetrospective study. Dogs with thyroid neoplasia were included when follow‐up information and formalin‐fixed paraffin‐embedded tumor samples were available. Immunohistochemistry (IHC) was performed for thyroglobulin, calcitonin, Ki‐67, and E‐cadherin. Correlation of tumor variables (diameter, volume, localization, scintigraphic uptake, thyroid function, IHC) with local invasiveness and metastatic disease was performed on all tumor samples. Forty‐four dogs treated by thyroidectomy were included in a survival analysis.ResultsFifty dogs (71%) had differentiated follicular cell thyroid carcinoma (dFTC) and 20 (29%) had medullary thyroid carcinoma (MTC). At diagnosis, tumor diameter (P = .007; P = .038), tumor volume (P = .020), tumor fixation (P = .002), ectopic location (P = .002), follicular cell origin (P = .044), and Ki‐67 (P = .038) were positively associated with local invasiveness; tumor diameter (P = .002), tumor volume (P = .023), and bilateral location (P = .012) were positively associated with presence of distant metastases. Forty‐four dogs (28 dFTC, 16 MTC; stage I–III) underwent thyroidectomy. Outcome was comparable between dogs with dFTC and MTC. Macroscopic (P = .007) and histologic (P = .046) vascular invasion were independent negative predictors for disease‐free survival. Although time to presentation, histologic vascular invasion and Ki‐67 were negatively associated with time to metastases, and time to presentation was negatively associated with time to recurrence, no independent predictors were found. E‐cadherin expression was not associated with outcome.Conclusions and Clinical ImportancePrognostic factors have been identified that provide relevant information for owners and clinicians.

Short survival time following palliative‐intent hypofractionated radiotherapy for non‐resectable canine thyroid carcinoma: A retrospective analysis of 20 dogs

“…For solitary tumors that are freely moveable, thyroidectomy is the treatment of choice with median survival times up to 3 years . Tumors determined to be non‐resectable due to large size or invasion into adjacent structures are often treated with radiotherapy.…”

Primary brain involvement of disseminated histiocytic sarcoma in a Rottweiler dog - histopathology, ¹⁸F-fluorodeoxyglucose positron emission tomography and 7 T-magnetic resonance imaging findings: a case report

“…Only seven sporadic cases have been reported in dogs (Moore et al 1984;Brown et al 2001;Campos et al 2014). Metastasis is common in thyroid carcinomas, and the most common metastatic sites are the lungs and regional lymph nodes (Liptak 2007;Campos et al 2014). In this case, thyroid tumour cells were observed in the lungs and in the submandibular and medial retropharyngeal lymph nodes.…”

“…Microscopically, medullary thyroid carcinoma could be misdiagnosed as follicular carcinoma of the compact type. Therefore, immunostaining for calcitonin or markers of parafollicular cells is important for identification of medullary carcinoma, whereas thyroglobulin immunoreactivity is specific for follicular carcinoma (Campos et al 2014). Based on microscopic observation alone the present case was initially diagnosed as a follicular-compact cellular type of carcinoma; however, the dog was definitively diagnosed as having MMFC based on dual staining for both thyroglobulin and calcitonin.…”

“…Although medullary thyroid carcinoma accounts for 16-36% of thyroid carcinomas in dogs, the incidence of canine MMFC is unknown (Leblanc et al 1991;Carver et al 1995;Campos et al 2014). Only seven sporadic cases have been reported in dogs (Moore et al 1984;Brown et al 2001;Campos et al 2014).…”

“…In this case, thyroid tumour cells were observed in the lungs and in the submandibular and medial retropharyngeal lymph nodes. A previous study demonstrated no difference in rates of metastasis between follicular and medullary carcinomas in dogs at diagnosis (Campos et al 2014). Further study is needed to investigate the prognostic relevance of differentiating MMFC from other types of thyroid tumours with immunostaining.…”