Primary melanoma thickness correlated with regional lymph node metastases

We studied 119 patients with stage I primary cutaneous malignant melanoma, who were undergoing regional lymph node dissection, to determine the relationship of lymph node metastases to thickness of the primary lesion. The lymph nodes in the dissection specimen were each evaluated by serial sections. None of the patients with lesions less than 1.0 mm thick had nodal micrometastases. When lesions exceeded 1.0 mm in thickness, there was no appreciable increase in the incidence of nodal metastases until a thickness greater than 4.0 mm was reached, in which cases the incidence of metastases was 50%. Predictive variables were determined by multiple logistic regression analysis. Only lesions that were at least 4.0 mm thick and were not located on the upper extremities were significant predictors of lymph node metastases; within this category there was a 64% incidence of lymph node metastases.