Inguinopelvic lymphadenectomy following positive inguinal sentinel lymph node biopsy in melanoma: True frequency of synchronous pelvic metastases

Background: True frequency of synchronous pelvic metastases with positive inguinal sentinel lymph node (SLN) biopsy is unknown. Role of pelvic dissection in the SLN era is unclear. Methods: From 1994 to 2004, 1 surgeon routinely performed nonselective, complete inguinopelvic lymphadenectomy after positive inguinal SLN biopsy. All cases were identified from a prospectively maintained database. Clinicopathologic features associated with pelvic disease were assessed. Results: A total of 40 patients with positive inguinal SLN underwent, without additional selection, 42 complete inguinopelvic lymphadenectomies. Median age was 46.5 years (range 25-79 years); 79% had lower extremity primaries. Median Breslow depth was 2.3 mm (range 1.0-10.0 mm), Clark's IV/V 98%, ulceration 26%. Frequency of synchronous pelvic disease upon completion lymphadenectomy was 5 of 42 (11.9%). Patients with and without pelvic disease were similar in age, sex, Breslow depth, Clark's level, ulceration, and mitoses. All 5 cases with pelvic metastases had extremity primaries (4 distal, 1 proximal). Of the 5, 3 (60%) had ≥3 total involved inguinal nodes, compared with only 1 (2.7%) of the 37 cases without pelvic disease (P = .003). Ratio of positive to total number inguinal nodes retrieved was >0.20 in 80% of cases with pelvic disease and 8.6% of cases without (P = .002). Upon lymphoscintigraphy review, secondary pelvic drainage was present in 80% of cases with pelvic disease compared with 56% of cases without pelvic disease, though the trend was statistically insignificant (P = .63). Conclusions: In this cohort of unselected, SLN-positive patients with complete inguinopelvic lymphadenectomy, frequency of synchronous pelvic disease was 11.9%. Patients with ≥ 3 total involved inguinal nodes or inguinal node ratio >0.20 appear more likely to harbor pelvic disease.