Sentinel node biopsy for squamous-cell carcinoma of the anus and anal margin

The majority of anal tumors are squamous-cell carcinomas. These may be tumors of the anal canal or margin. They are best treated by combination of chemotherapy and radiotherapy. T1 and T2 tumors in this regime do not receive radiotherapy to the inguinal regions despite approximately 5 to 10 percent incidence of inguinal lymph node involvement. If the nodal status of the inguinal region could be accurately assessed, then a more tailored radiotherapy regime may be given. This article describes a novel method of assessment of the status of the inguinal lymph nodes in patients.

Patients with anal squamous-cell carcinoma had four injections of 0.2 ml of antimony sulfide (30 MBq) around the tumor. Under a gamma camera, a distant high-intensity signal was located, and this point was marked on the overlying skin using an indelible ink pen. In the operating theater, patent blue dye was injected all around the tumor. The localized lymph node was removed and sent for histopathology.

This procedure was performed on 12 patients. The sentinel node was localized to the inguinal region and removed in eight of these patients. In two patients, metastatic squamous-cell carcinoma was identified histologically in the sentinel node.

We advocate that this as a safe technique for detecting metastatic disease in the inguinal nodes in patients with anal squamous-cell carcinoma.