Do micromorphometric features of metastatic deposits within sentinel nodes predict nonsentinel lymph node involvement in melanoma?

INTRODUCTION: Multiple attempts have been made to identify melanoma patients with a positive sentinel lymph node (SLN) who are unlikely to harbor residual disease in the nonsentinel lymph nodes (NSLN). We examined whether the size and location of the metastases within the SLN may help further stratify the risk of additional positive NSLN.

METHODS: A review of our Institutional Review Board (IRB)-approved melanoma database was undertaken to identify all SLN positive patients with SLN micromorphometric features. Univariate logistic regression techniques were used to assess potential significant associations. Decision tree analysis was used to identify which features best predicted patients at low risk for harboring additional disease.

RESULTS: The likelihood of finding additional disease on completion lymph node dissection was significantly associated with primary location on the head and neck or lower extremity (P = 0.01), Breslow thickness >4 mm (P = 0.001), the presence of angiolymphatic invasion (P < 0.0001), satellitosis (P = 0.004), extranodal extension (P = 0.0002), three or more positive SLN (P = 0.02) and tumor burden within the SLN >1% surface area (P = 0.004). Sex, age, mitotic rate, ulceration, Clark level, histologic subtype, regression, and number of SLN removed had no association with finding a positive NSLN. Location of the metastases (capsular, subcapsular or parenchymal) showed no correlation with a positive NSLN. Decision tree analysis incorporating size of the metastatic burden within the SLN along with Breslow thickness can identify melanoma patients with a positive SLN who have a very low risk of harboring additional disease with the NSLN.

CONCLUSION: Size of the metastatic burden within the SLN, measured as a percentage of the surface area, helps stratify the risk of harboring residual disease in the nonsentinel lymph nodes (NSLN), and may allow for selective completion lymphadenectomy.