(0677) Management and Outcomes of Non-Mapping Lymphoscintigraphy in Cutaneous Malignancy of the Head and Neck

Introduction: A key modality in evaluating N stage for cutaneous malignancies is lymphoscintigraphy as part of a sentinel lymph node biopsy (SNLB). Occasionally, lymphoscintigraphy is performed, and the scan is unable to identify a sentinel node. These rare non-mapping lymphoscintigraphy (NML) cases pose a diagnostic challenge for the surgeon.

Methods: We performed a retrospective chart review study of adult patients (> 18 years old) who underwent SLNB at our tertiary care center for a cutaneous malignancy of the head and neck over a 13-year period from 2010-2023. We reviewed disease characteristics, the methodology used to mitigate the lack of lymphoscintigraphy by surgeon, and outcomes.

Results: There were 49 patients with NML out of 430 total lymphoscintigraphy scans performed for SNLB for head and neck cutaneous malignancy (11.9%). The median age was 77 years (IQR 68 to 82). Of these, 37 were for melanoma (75%), 7 were for cutaneous squamous cell carcinoma (cSCC, 14%), and 5 were for Merkel cell carcinoma (MCC, 10%). Management varied for the management of these patients. For most cases, surgeons opted to inject methylene blue dye and use a gamma probe intra-operatively to attempt to identify a SLN (31 patients, 48%). In 18 patients (37%), clinical observation with serial ultrasound was performed. There was a 32% local recurrence rate for patients with melanoma (12/37 patients). There was a 43% local recurrence rate for patients with cSCC (3/7 patients). There was a 20% local recurrence rate for patients with MCC (1/5 patients). There was a 27% distant metastasis rate for patients with melanoma (10/37 patients). There were no distant metastasis seen in the cSCC patients). There was a 20% distant metastasis rate for patients with MCC (1/5 patients).

Conclusions: Negative lymphoscintigraphy is a diagnostic dilemma in the management of cutaneous malignancy in the head and neck. In this cohort, these patients were at high risk for recurrence and distant metastasis.