Long-term survival data on sentinel lymph node biopsy in anorectal melanoma

Abstract

Sentinel lymph node (SLN) biopsy is currently the method of choice to assess the nodal status of patients with cutaneous melanoma. It has largely replaced elective lymph node dissection, sparing patients with negative SLN the morbidity associated with a complete regional lymphadenectomy. However, experience with the SLN procedure in anal melanoma has been limited to a few reported cases, probably due to the rarity of this tumor. Anorectal melanoma (AM) accounts for 1% of all anorectal malignancies. Most patients are diagnosed with advanced disease and have poor 5-year survival (0–22%). Although surgery is the mainstay of treatment, there appears to be no difference in survival whether wide local excision (LE) or abdominoperineal resection is performed. Locoregional metastases are frequent and may involve both inguinal and pelvic lymph nodes [1]. In this letter, we report a case of AM that had an unexpectedly favorable clinical evolution. Our patient was an 89-year-old diabetic woman presenting with an anal lesion that she first noticed 8 months earlier. It was a non-pigmented nodule, 3 cm in diameter, located at the dentate line. Inguinal palpation was unremarkable. Biopsy of the lesion showed an undifferentiated tumor, but the immunohistochemical analysis was positive for S-100 protein and HMB-45, thus establishing the diagnosis of AM. Staging workup did not detect metastases. Considering the general condition of the patient, treatment by wide local excision of the tumor along with SLN biopsy was proposed. Twelve hours before surgery, Dextran 500 labeled with Technetium-99 m was injected into the parenchyma around the primary tumor. Subsequently, lymphoscintigraphy demonstrated a SLN (hot spot) in the right groin (Fig. 1). On the following day, patent blue dye was injected at the same sites around the tumor. The inguinal area was scanned with a gamma probe, and a 3-cm incision was made over the hot spot. During inguinal dissection, the blue color of the SLN served as a guide to its location. After removal of the SLN, excision of the AM was performed. Histopathology and immunohistochemistry of the surgical specimen confirmed AM with tumor-free resection margins. The SLN was diagnosed as positive for metastatic melanoma. The patient refused any additional treatment but remained free of disease after 52 months of follow-up. Although the SLN procedure has been successfully tested in other anal tumors, the investigation into the SLN in AM is currently limited to 6 cases [1–4]. Long-term survival was not documented in any of them. In our patient, we used the same SLN procedure we had previously investigated in cases of epidermoid carcinoma of the anal canal and rectal adenocarcinomas invading the dentate line [5, 6]. Our technique, which consisted of a combination of blue dye and radio-colloid, was effective in sampling a SLN from the left inguinal area. Moreover, it allowed the detection of metastatic deposits within the SLN, which D. C. Damin (&) M. A. Rosito Division of Coloproctology, Hospital de Clinicas de Porto Alegre (Sala 600) and Department of Surgery, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos 2350, 90035 903 Porto Alegre, RS, Brazil e-mail: damin@terra.com.br