Is a solitary inguinal lymph node metastasis from adenocarcinoma of the rectum really a metastasis?

Metastatic involvement of inguinal lymph nodes (ILN) from rectal adenocarcinoma is unusual, particularly without signs of distant spread to other organ sites. By current convention, ILN involvement, including solitary involvement, is classified as metastatic disease (M). However, anecdotal reports suggest that such patients are a distinct entity and should be managed differently. The aim of this study was to gain further insight regarding this seemingly distinct patient subset.

This case series provides a descriptive report of patients with rectal adenocarcinoma and solitary inguinal lymph node metastasis (SILNM).

Upon retrospective review of medical records from 4480 patients with rectal adenocarcinoma seen at Mayo Clinic Rochester from 1995 to 2004, six patients (0.13%) with SILNM were identified. Three had metachronous and three had synchronous SILNM (four left sided, one right sided, and one bilateral). The mean age at SILNM diagnosis was 61.3 years, and three patients had originally stage II (and three had stage III disease). Five patients received concurrent chemo-radiation therapy and one declined treatment. Among those with metachronous SILNM, the mean survival after diagnosis of rectal cancer was 42 months. By comparison, all three patients with synchronous SILNM were still alive after a mean duration of 40 months of follow up.

Solitary involvement of ILNs might represent a distinct subset of patients with metastatic rectal adenocarcinoma who have a more favourable prognosis. If confirmed by larger studies, our data suggest that alternate management algorithms might be reasonable for such patients.