Size of metastasis in the sentinel node predicts additional nodal involvement in penile carcinoma

PURPOSE: The majority of patients with penile cancer with a tumor positive sentinel node do not benefit from complementary lymph node dissection because of absent additional involved nodes. We analyzed factors that may determine the involvement of additional nodes. MATERIALS AND METHODS: A total of 158 patients with clinically node negative penile carcinoma underwent sentinel node biopsy. Complementary inguinal lymph node dissection was performed when the sentinel node was tumor positive. The size of the sentinel node metastasis was measured and classified as micrometastasis--2 mm or less, or macrometastasis--more than 2 mm. Sentinel and dissection specimen nodes were step-sectioned. Factors were analyzed for their association with additional nodal involvement, including stage, diameter, grade, absence or presence of vascular invasion of the primary tumor, and sentinel node metastasis size. RESULTS: Tumor positive sentinel nodes were found in 46 groins and complementary lymph node dissection was performed. Nine of these 46 groins (20%) contained additional involved lymph nodes. On univariate and multivariate analyses the size of the sentinel node metastasis proved to be the only significant prognostic variable for additional lymph node involvement (each p = 0.02). None of the 15 groins with only micrometastasis in the sentinel node contained additional involved nodes. CONCLUSIONS: In penile carcinoma additional nodal involvement was related to the size of the metastasis in the sentinel node. Sentinel node micrometastasis was not associated with other involved lymph nodes. This finding suggests that these patients can be spared complementary lymph node dissection.