Some surgeons question the survival advantage of ilioinguinal lymphadenectomy for metastatic melanoma because they believe that deep nodal involvement signifies a poor prognosis that is unchanged by surgery. However, several series, including our own, have reported 5-year survival rates reaching 30%. New adjuvant therapies may further improve survival after ilioinguinal lymphadenectomy, but this applies only to nodal basins with metastatic disease. We hypothesized that the node of Cloquet accurately reflects the pathologic status of the iliac/obturator nodes, allowing deep pelvic lymphadenectomy to be selectively performed.Between 1972 and 1998, 691 patients with primary cutaneous melanoma underwent both elective and therapeutic complete (superficial and deep) ilioinguinal lymphadenectomy. Of the 204 (30%) patients with tumor-positive inguinal and/or iliac/obturator nodes, 68 had a node of Cloquet identified during pathologic review of the lymphadenectomy specimen. Chart and computer database review of these 68 patients was undertaken to determine the association between the tumor status of Cloquet's node and that of deep pelvic nodes. Immunohistochemical analysis was performed on eight of 11 negative Cloquet's nodes in patients with positive iliac/obturator nodes. Paraffin blocks of the other three negative nodes of Cloquet were unavailable for immunohistochemistry, and they were excluded from analysis.Tumor-positive deep nodes were identified in the lymphadenectomy specimen from 20 of 30 (67%) patients with a positive Cloquet's node and from eight of 35 (23%) patients with a negative Cloquet's node (P = 0.0019). Re-examination of these eight tumor-negative Cloquet's nodes using immunostaining with S-100 and HMB45 identified tumor in 3 nodes, increasing the sensitivity of Cloquet's node for predicting deep nodal metastases from 71% to 82%. The 6.8 odds ratio of positive iliac/obturator nodes given a positive node of Cloquet increased to 12.4 after immunohistochemical analysis. The positive and negative predictive values were also enhanced from 67% to 70% and 77% to 84%, respectively.The tumor status of the node of Cloquet significantly reflects the tumor status of the iliac/obturator nodes, particularly when Cloquet's node is examined by immunohistochemical analysis. The node of Cloquet assumes the role of the sentinel node in patients whose superficial inguinal lymph nodes drain through Cloquet's node to the iliac/obturator nodes.