Abstract Aim The significance of lymphadenectomy and its indications in patients with inguinal lymph node metastasis (ILNM) of anorectal adenocarcinoma is unclear. This study aimed to clarify the surgical outcomes and prognostic factors of inguinal lymphadenectomy for ILNM. Method This study included patients who underwent surgical resection for ILNM of rectal or anal canal adenocarcinoma with pathologically positive metastases between 1997 and 2011 at 20 participating centres in the Study Group for Inguinal Lymph Node Metastasis from Colorectal Cancer organized by the Japanese Society for Cancer of the Colon and Rectum. Clinicopathological characteristics and short‐ and long‐term postoperative outcomes were retrospectively analysed. Results In total, 107 patients were included. The primary tumour was in the rectum in 57 patients (53.3%) and in the anal canal in 50 (46.7%). The median number of ILNMs was 2.34. Postoperative complications of Clavien–Dindo Grade III or higher were observed in five patients. The 5‐year overall survival rate was 38.8%. Multivariate analysis identified undifferentiated histological type ( P &lt; 0.001), pathological venous invasion ( P = 0.01) and pathological primary tumour depth T0–2 ( P = 0.01) as independent prognostic factors for poor overall survival. Conclusion The 5‐year overall survival after inguinal lymph node dissection was acceptable, and it warrants consideration in more patients. Further larger‐scale studies are needed in order to clarify the surgical indications.

Short‐ and long‐term outcomes of surgical treatment for inguinal lymph node metastasis in rectal and anal canal adenocarcinoma