The effect of lymph node metastasis on local tumor control and distant failure in patients with anorectal melanoma has not been fully studied. Understanding the significance of lymphatic dissemination might assist in stratifying patients for either organ preservation or radical surgery.

A retrospective review of all patients with anorectal melanoma who underwent surgery at our institution between 1985 and 2010. Abdominoperineal resection (APR) was performed in 25 patients (39 %), and wide local excision (WLE) in 40 (61%). Extent of primary surgery and locoregional lymphadenectomy (mesorectal vs. inguinal vs. none) and pattern of treatment failure were analyzed. Recurrence-free survival (RFS) and disease-specific survival (DSS) were calculated.

In patients undergoing APR, DSS was not associated with presence (29 %) or absence (71 %) of metastatic melanoma in mesorectal lymph nodes. There was a trend toward improved DSS in patients with clinically negative inguinal lymph nodes (n = 17) compared with patients with proven inguinal metastasis (n = 6; P = 0.12). Type of surgery (WLE vs. APR) was not associated with subsequent development of distant disease. Twelve patients (18 %) had synchronous local and distant recurrence. Synchronous recurrence was not associated with surgical strategy used to treat primary tumor (P = 0.28). Perineural invasion (PNI) was significantly correlated with RFS (P = 0.002).

Outcome following resection of anorectal melanoma is independent of locoregional lymph node metastasis; lymphadenectomy should be reserved for gross symptomatic disease. PNI is a powerful prognostic marker warranting further exploration in clinical trials.