Positive Lymph Node Counts in American Thyroid Association Low-Risk Papillary Thyroid Carcinoma Patients.

Abstract

Current American Thyroid Association (ATA) guidelines state that patients with intermediate-risk papillary thyroid cancer (PTC) may benefit from remnant ablation. One criterion for intermediate-risk classification is >5 positive lymph nodes (LNs). We investigate whether performing step-sectioning of LNs increases the metastatic detection rate, thereby influencing ATA risk of recurrence (ROR) classification. A retrospective review was conducted of cases in which ≥ 5 LNs were removed during thyroidectomy and ≤5 LNs were found positive for PTC. Step-sectioning was performed on the original tissue blocks. All slides were re-reviewed by a senior pathologist. Twenty patients met study criteria. Step-sectioning significantly increased LN yield compared to standard sectioning. In total, we found 12 new positive lymph nodes; seven (58%) were in totally new lymph nodes, while five (42%) were in lymph nodes previously read as negative. All newly discovered metastases were classified as micrometastases (≤2mm). Of the 15 patients originally classified as low-risk, the step-sectioning protocol impacted two patients (13%), increasing ROR stratification. Intensive step-sectioning reveals additional micrometastases. More detailed analysis did not identify clinically significant nodal disease likely to impact the clinical course of patients in this study. Our study supports current standards of pathology specimen handling related to LN assessment and the impact on ATA ROR classification. Nonetheless, it is important for clinicians to understand their institution's sectioning protocol utilized to report positive and total LN counts, which could impact ATA risk stratification and denote the comprehensive nature of the LN dissection that was performed.