Sentinel Lymph Node Biopsy for Cutaneous Squamous Cell Carcinoma on the Head and Neck.

IMPORTANCE: Metastasis of cutaneous squamous cell carcinoma (SCC) to the nodal basin is associated with a poor prognosis. The role of sentinel lymph node biopsy (SLNB) for regional staging in patients diagnosed with SCC is unclear.

OBJECTIVE: To evaluate a single institution's experience with use of SLNB for regional staging of SCC on the head and neck.

DESIGN, SETTING, AND PARTICIPANTS: A retrospective review of 53 patients who were diagnosed with SCC on the head and neck, at high risk for nodal metastasis based on National Comprehensive Cancer Network (NCCN) risk factors, and treated with wide local excision (WLE) and SLNB from December 1, 2010, through January 30, 2015, in a single academic referral center was performed. The follow-up period ended November 5, 2015. Sentinel lymph node biopsy paraffin blocks were retrieved and processed retrospectively with serial sectioning and immunohistochemical analysis (IHC) in cases with nodal recurrence following a negative SLNB.

MAIN OUTCOMES AND MEASURES: Sentinel node (SN) identification rate, SLNB positivity rate, local recurrence, regional nodal recurrence, and distant recurrence.

RESULTS: In 53 patients with 54 tumors the SN identification rate was 94%. The SLNB positivity rate was 11.3%. On more thorough tissue processing and IHC, metastatic SCC was identified in 2 of 5 (40%) cases previously deemed negative. After reclassification of these cases, the adjusted SLNB positivity rate was 15.1%. The adjusted rate of false omission was 7.1% (95% CI, 2%-19%). Nodal disease developed in 20.8% overall. Angiolymphatic invasion (Cohen d, 3.52; 95% CI, 1.83-5.21), perineural invasion (Cohen d, 0.81; 95% CI, 0.09-1.52), and clinical size (Cohen d, 0.83; 95% CI, 0.05-1.63) were associated with the presence of nodal disease.

CONCLUSIONS AND RELEVANCE: Rigorous study of SLNB for cutaneous SCC incorporating prospectively-collected comprehensive data sets based on standardized treatment algorithms is justified with potential to modify clinical practice. Our study demonstrates the critical importance of serial sectioning and IHC of the SLNB specimen for accurate diagnosis. Use of the NCCN guidelines may facilitate identification of patients with SCC at high risk for nodal metastasis.