Histological features of melanoma sentinel lymph node metastases associated with status of the completion lymphadenectomy and rate of subsequent relapse

Background: The current recommendation for patients with cutaneous melanoma and a positive sentinel lymph node (SLN) biopsy is a completion lymph node dissection (CLND). This study sought to define a population of SLN-positive patients, based on their histological pattern of SLN metastases, who may not require CLND. Methods: All patients with SLN-positive cutaneous melanoma who underwent CLND between March 1999 and December 2004 at a single academic institution were enrolled. Metastatic deposits in the SLN were categorized by their histological zone of involvement (subcapsular, parenchymal and/or sinusoidal). Logistic regression was used to examine the effect of SLN zone, size of nodal metastases, and other histological factors on CLND positivity. Kaplan-Meier and Cox models were used to study disease recurrence. Results: A total of 127 patients were included, and 15.8% had positive non-sentinel nodes. In adjusted analyses, the size of the largest tumor deposit in the SLN was the only factor associated with CLND status. No patients with a tumor deposit <= 0.20 mm had a positive CLND. Although a specific zone of tumor involvement was not predictive of CLND status, involvement of all three zones was independently associated with increased recurrence. Size of the largest tumor deposit was also associated with recurrence, with no recurrences in patients with nodal deposits <= 0.20 mm. Conclusion: Histologic features of tumor metastases in positive SLN may be useful in defining a population of patients who may be spared CLND and a group at high risk of recurrence.