Treatment and Prognostic Significance of Positive Interval Sentinel Nodes in Patients with Primary Cutaneous Melanoma

Background. Interval sentinel nodes (SNs) are lymph nodes receiving direct lymphatic drainage from a primary site and lying between the tumor and a recognized node field. It is not clear what further nodal surgery should be performed when interval nodes are found to contain micrometastatic disease. In this study, the incidence, location, and treatment of interval SNs in melanoma patients were analyzed to develop recommendations regarding the treatment of patients with interval SNs. Methods. A retrospective review was undertaken of all patients with primary cutaneous melanoma who underwent lymphoscintigraphy at a single institution between 1992 and 2007. Data concerning the primary melanoma, location of SNs, treatment and survival were analyzed. Results. Of 4895 patients who had a lymphoscintigram during the study period, 442 (9.0%) had an interval SN identified on lymphoscintigraphy. Interval SNs occurred significantly more often in patients with melanomas on the posterior trunk than in those with melanomas at other sites (P < 0.001). A total of 197 patients (44.6%) with an identified interval SN underwent excision biopsy of the node. Of the 16 patients found to have metastatic melanoma in their interval SN, four also had negative SNs in a recognized lymph node field, and no other positive nodes were found on completion lymphadenectomy. Conclusions. Interval SNs are present in approximately 1 in 10 melanoma patients but are about half as likely to contain metastases as SNs in recognized node fields. If a positive interval SN is found, completion lymphadenectomy of the recognized lymph node field is only recommended if a SN in this field is also positive.