Resection of Thyroid Tumors with Vascular Invasion in Dogs

In the literature

Latifi M, Skinner OT, Spoldi E, et al. Outcome and postoperative complications in 73 dogs with thyroid carcinoma with gross vascular invasion managed with thyroidectomy. Vet Comp Oncol. 2021;19(4):685-696.

The Research …

Limited information exists regarding resection of thyroid tumors with gross vascular invasion in dogs. Presence of gross vascular invasion indicates a worse prognosis in humans with thyroid carcinoma at risk for increased distant metastasis.¹

This retrospective study assessed the records of 73 dogs from 10 veterinary referral hospitals that underwent preoperative contrast-enhanced cervical CT imaging, thoracic imaging, and thyroidectomy for thyroid carcinoma with gross vascular invasion.

Dogs had long survival times (median, 621 days) and limited complications following thyroidectomy with en bloc resection of tumor thrombi. Two dogs required transfusion for intraoperative bleeding, and 2 dogs died postoperatively before discharge. Factors impacting disease-specific survival were not found. 

Gross tumor vascular invasion was identified on preoperative CT imaging in half of the dogs and was an intraoperative discovery in the remaining half. Metastasis was found in 44% of dogs that underwent lymph node resection, suggesting there is value in lymph node staging, although the impact on overall patient survival is unclear.

Thyroid carcinoma disease progressed slowly. Locoregional tumor recurrence was suspected and confirmed with fine-needle aspiration in 9.6% of the dogs (median, 238 days postoperative). The one-year postoperative disease-specific survival rate was 82.5%. 

Gross vascular invasion of thyroid tumors is not a contraindication for thyroidectomy in dogs, and thyroidectomy remains an option for treatment of this disease; the role of adjuvant chemotherapy remains uncertain.

… The Takeaways

Key points to put into practice:

• Conservative marginal (vs wide) excision of thyroid carcinoma can be effective and limit postoperative morbidity risk because of the low tumor recurrence rate for this disease.

• Preoperative and immediate postoperative laryngeal function examination is encouraged due to tumor-related and iatrogenic risks to the recurrent laryngeal nerve.

• Thyroidectomy is indicated for mobile tumors, including those with findings of gross vascular invasion. For fixed thyroid tumors, anesthetized tumor palpation and cervical CT findings may favorably influence consideration for surgical versus nonsurgical treatment. Cervical contrast CT imaging reduces the potential for unexpected intraoperative findings (eg, tumor thrombi) and aids in regional lymph node staging.