Tumor classification in well-differentiated thyroid carcinoma and sentinel lymph node biopsy outcomes: A direct correlation

Background: Predicting locoregional metastasis in well-differentiated thyroid carcinoma (WDTC) is a challenge for thyroid cancer surgeons. Sentinel lymph node biopsy (SLNB) has been shown to be an effective predictive tool. To our knowledge, primary tumor (T) classification has yet to be studied with regard to SLNB. We hypothesized that larger primary tumors would correlate with the rate of malignancy in SLNBs. Methods: A retrospective chart review was conducted on patients operated for WDTC at the McGill Thyroid Cancer Center over a 36-month period. Patients who underwent a total thyroidectomy and SLNB for WDTC were included in this study. Results: A total of 311 patients were included and separated into two groups (236 negative and 75 positive SLNBs). Among patients with negative SLNBs, 65% had T1 primary tumors, 17% T2, 16% T3, and 2% T4, whereas 18% of patients with positive SLNBs had T1 primary tumors, 5% T2, 45% T3, and 32% T4 (p<0.001). Patients under the age of 45 years had a higher rate of positive SLNs (36% in those <45 years vs. 17% in those ≥45 years; p<0.001). Conclusions: Age (<45 years) and higher T category were found to be associated with a higher rate of positive SLNBs.