Sentinel lymph node metastasis in anal melanoma: a case report

Anal melanoma represents only 1% of all melanomas. Owing to delayed diagnosis and early metastasis, the prognosis is uniformly poor. Sentinel lymph node (SLN) biopsy has become the preferred method of nodal staging method for cutaneous melanoma. The role of SLN biopsy for staging of anal melanoma remains unclear. We report a 39-yr-old Caucasian woman who presented with a history of chronic hemorrhoidal pain. She noted a pedunculated peri-anal mass associated with bleeding. Upon biopsy, the lesion was found to be a 6-mm thick primary anal melanoma. There was no evidence of metastatic disease on preoperative imaging studies. She underwent wide local excision of the peri-anal site of the primary melanoma and intra-operative lymphatic mapping with both isosulfan blue and filtered technetium sulfur colloid. With the guidance a lymphoscintigram, ipsilateral inguinal sentinel lymphadenectomy identified five nodes, all of which were both "hot" and blue. One node was found to have a 1-mm metastatic deposit. Subsequently, the patient was treated with adjuvant radiation therapy to the primary site as well as to the superficial and deep inguinal nodal basins. She also received four cycles of biochemotherapy. SLN biopsy appears feasible for staging the superficial inguinal lymph nodes in patients with anal melanoma. However, the impact of SLN biopsy, early detection of occult metastasis, and adjuvant systemic and radiation therapy on the long-term survival of patients with anal melanoma is uncertain.