The term microinvasive carcinoma is inappropriate when applied to all vulvar cancers less than or equal to 5 mm thick because approximately 50% of vulvar carcinomas are no thicker than 5 mm and 20% of those superficial tumors metastasize to the lymph nodes. The significant predictors of groin node metastases in patients with superficial vulvar cancer are tumor thickness, histologic grade (proportion of undifferentiated tumor pattern), capillary-like space involvement with the tumor, clitoral or perineal location, and clinically suspicious nodes, according to the linear logistic model analysis of clinicopathologic data in 272 women. No lymph node metastases occurred in approximately one fourth of patients with a combination of low-risk factors: no clinically suspicious nodes, negative capillary-like space, and nonmidline vulvar cancers that were either grade 1 and 1 to 5 mm thick or grade 2 and 1 to 2 mm thick. In contrast, all 10 patients with clinically suspicious nodes and grade 4 tumors had positive groin nodes. The risk of lymph node metastases is best determined by simultaneous evaluation of all risk factors rather than a single factor such as tumor thickness.