Lymphatic mapping and sentinel lymphadenectomy after wide local excision of primary melanoma

Background: Lymphatic mapping and sentinel lymphadenectomy (LM/SL) are generally avoided in patients who have already undergone wide local excision (WLE) of a primary melanoma, because of concern that disruption of the cutaneous lymphatics might alter lymphatic flow to the sentinel node. We reviewed carefully chosen patients who had undergone LM/SL after WLE to identify circumstances that might make this approach otherwise safe and clinically accurate. Study Design: From our melanoma database of 8,300 patients, of whom 1,015 had undergone LM/SL, we retrospectively identified 47 patients who had previously undergone WLE. Patient and tumor characteristics were collected and compared with followup data from clinic files. Results: Median WLE surgical margins before LM/SL were 2.0 cm and most patients had extremity lesions. Eleven of the 47 patients (23%) had tumor-involved sentinel nodes, and 8 of these patients (73%) had a solitary nodal metastasis. With a median followup period of 36 months, 3 sentinel node-negative patients developed nodal recurrences. Two of these patients had positive sentinel nodes on pathology re-review and were not considered failures of the lymphatic mapping surgical procedure. The third patient developed in-transit metastases and delayed nodal recurrence. An additional patient, who had a primary tumor on the trunk, developed a nodal recurrence in the basin opposite that identified by lymphoscintigraphy. The overall error rate of the technique was 4 in 36 (11%). This included 2 pathology misdiagnoses (5.6%), 1 nodal recurrence associated with in-transit regional metastases (2.8%), and 1 lymphatic mapping error (2.8%). Conclusions: LM/SL can be cautiously performed in patients who have undergone previous WLE if the primary resection margin was no greater than 2.0 cm and the primary was not in a region of ambiguous drainage. Lymphatic mapping may be inaccurate when melanomas have been resected with large margins, especially if the wound was closed with rotation flaps, and when melanomas are on the head and neck or trunk regions.