Background: Lymphatic mapping and sentinel lymph node biopsy (SLNB) has become the standard of care for the evaluation and staging of intermediate risk melanoma and merkel cell carcinoma. The high density of lymph nodes in the head and neck results in variable draining patterns and may result in nonlocalization of a sentinel node and the inability to perform SLNB. Previous literature has cited a nonlocalization rate of 6.8%. As technology advances and new dyes are used, we aim to present an updated incidence of nonlocalization in head and neck melanoma and merkel cell carcinoma and the outcomes in these situations.
Methods: Upon IRB approval, a review of 357 patients who underwent lymphoscintigraphy in the University Hospitals Cleveland Medical Center Department of Nuclear Medicine between the years 2012-2015 were queried, and those whose indication was for a head and neck melanoma or merkel cell carcinoma were included and underwent retrospective chart review. Of note, in 2013 our institution switched from using filtered sulfur-colloid (passive transport) to Lymphoseek (Tc-99m tilmanocept), a receptor-targeted lymphatic mapping agent. Patient demographic data, clinical characteristics, lymphoscintigraphy details, treatment details, and survival were analyzed.
Results: 79 consecutive patients who underwent lymphoscintigraphy for head and neck melanoma or Merkel cell carcinoma were identified. The overall rate of nonlocalization of sentinel nodes was 8.9% (n=7). The rate of nonlocalization was 7.5% (n=3) using the passive transport sulfur-colloid injection and 10.8% (n=4) using the active transport Lymphoseek injection. Of those that failed to localize a sentinel node on lymphoscintigraphy, 71% (n=5) were melanoma. The location of lesions included forehead (n=2), cheek (n=2), postauricular (n=1), scalp (n=1) and nose (n=1). All underwent wide local excision. Despite nonlocalization, lymph nodes were removed in two situations, one showing a benign lymph node and the other showing multiple lymph nodes with metastatic merkel cell. Three patients (43%) experienced locoregional or metastatic recurrence, of which one is currently living without evidence of disease, one is alive with metastatic disease, and one died after metastasis.
Conclusions: In a series of patients treated with preoperative lymphoscintigraphy for head and neck melanoma or merkel cell carcinoma at a single institution, the rate of nonlocalization was 8.9%, slightly higher than previously reported. This data illustrates that patients who are not able to undergo localization are still at risk for the development of regional disease and close observation and/or elective treatment of the neck should be considered. A larger multi-institutional study will also be necessary to elucidate which patients are at risk for nonlocalization and what interventions can be done to minimize its occurrence.