Sentinel lymph node procedure in patients with epidermoid carcinoma of the anal canal: early experience

This study was conducted to assess the feasibility of the sentinel lymph node procedure in patients with epidermoid carcinoma of the anal canal.

Between February 2001 and November 2002, 14 patients with epidermoid carcinoma of the anal canal and no clinical evidence of inguinal involvement were prospectively enrolled in the study. The sentinel lymph node procedure consisted of a combination of preoperative lymphoscintigraphy with technetium 99m dextran 500 injected around the tumor and intraoperative detection of the sentinel node with a gamma probe. Patent blue V dye was also injected at the periphery of the tumor to facilitate direct identification of the blue-stained lymph node. After removal, the sentinel node was studied by hematoxylin and eosin staining and immunohistochemistry for pancytokeratins (antigen A1 and A3).

Detection and removal of sentinel lymph nodes was possible in all patients. There was no correlation between tumor size and pattern of lymphatic drainage to the groin. Tumors located in the midline of the anal canal gave rise to bilateral sentinel nodes in eight of nine cases. In total, 23 sentinel lymph nodes were removed. One patient (7.1 percent) had a node identified as positive for metastatic carcinoma on immunohistochemical staining. Surgical complications were minimal.

The standardized technique was safe and highly effective in sampling inguinal sentinel lymph nodes in carcinoma of the anal canal. It also proved to be useful as an instrument to detect micrometastatic deposits in clinically normal nodes. Our early results suggest the sentinel lymph node procedure may have a role in guiding a more selective approach for patients with anal cancer. Additional studies in a larger patient population to determine the sensitivity and specificity of this method are warranted.