Accuracy of Sentinel Lymph Node Biopsy to Predict Nodal Metastasis in Head and Neck Merkel Cell Carcinoma

Merkelcell.org Summary

Patients with Merkel cell carcinoma (MCC) often have a procedure called a sentinel lymph node biopsy (SLNB). In this test, doctors remove the first lymph nodes that cancer would likely spread to and check them under a microscope for MCC that cannot be seen on scans. This helps doctors understand how far the MCC has spread and decide on the best treatment.

This study looked at whether SLNB was reliable specifically for patients whose MCC tumors were originally on the head/neck. They looked at 86 MCC patients with head/neck MCC and found that 69 of them (80%) had a SLNB. Hidden cancer in the lymph nodes was found in about 30% of patients, and the SLNB correctly identified 53% of the patients who truly had MCC in their lymph nodes. Among patients whose SLNB results were negative, about 90% truly did not have MCC in their lymph nodes. However, in about 10% of cases the test missed cancer that was actually present (called a false negative), meaning MCC later appeared in the lymph nodes despite the earlier negative SLNB.

The procedure could not be successfully completed in about 30% of patients and was more likely to fail in older patients, women, and certain tumor locations.

Overall, SLNB is still helpful for patients with head and neck MCC because it can find hidden cancer that scans might miss. However, in this area of the body, the test is less reliable and sometimes fails. Because of this, patients whose SLNB fails may need closer follow-up with physical exams, imaging scans, and possibly additional treatment to make sure the MCC does not spread.

Abstract

Importance: Merkel cell carcinoma (MCC) is a rare neuroendocrine malignant neoplasm often affecting the head and neck. Sentinel lymph node biopsy (SLNB) is routinely performed; however, the accuracy and reliability of SLNB for head and neck MCC remains unknown.

Objective: To determine the accuracy of SLNB in head and neck MCC and inform pre- and post-SLNB risk stratification.

Design, setting, and participants: This was a single-center cohort study of patients with clinically node-negative head and neck MCC who underwent SLNB from January 2006 to January 2025; median (IQR) follow-up was 1.9 (0.8-4.6) years. Data analysis was conducted from April to November 2025.

Interventions: SLNB outcome and nodal disease status.

Main outcomes and measures: SLNB accuracy measured by sensitivity, negative predictive value (NPV), and false negative (FN) rate. FN SLNB was defined as regional nodal recurrence at the first site of recurrence after a negative SLNB without concurrent local or in-transit recurrence. Factors associated with failed SLNB (defined as nonvisualization on lymphoscintigraphy, inability to identify the sentinel lymph node intraoperatively, or absence of nodal tissue in the pathology specimen) were evaluated using effect-size measures. Cox proportional hazards model identified factors associated with nodal disease, comparing patients who developed nodal disease (identified by SLNB or subsequent clinical and/or imaging evaluation) with those who did not develop nodal disease during follow-up.

Results: Of 86 participants (mean [SD] age, 75.6 [9.6] years; 36 female [41.9%] and 50 male [58.1%] individuals) with clinically node-negative head and neck MCC, 69 (80.2%) underwent SLNB. Occult nodal disease was identified in 19 participants (27.5%). SLNB sensitivity was 52.6% (10 of 19 patients), NPV was 88.6% (31 of 35 patients), and FN rate was 26.7% (4 of 15 patients). SLNB failed in 29.0% (20 of 69 patients), with tumor location, female sex, and older age having medium to large effect on SLNB failure. Lymphovascular invasion, infiltrative growth pattern, and tumor size had the largest effect size on nodal disease with Cox analysis.

Conclusions and relevance: In this large single-site cohort study, SLNB remained a useful tool in head and neck MCC, identifying more than half of occult nodal disease. Given reduced performance in this region, patients with failed SLNB or negative SLNB plus high-risk features may benefit from tailored management, including intensified therapy and surveillance.