Abstract
We present a case of primary malignant melanoma in the anorectal area in a 67-year-old man, who presented with a three-month history of anal bleeding and prolapsed tumor. Colonoscopic examination disclosed a blackish blue tumor just on the dentate line, and the biopsy specimen revealed malignant melanoma. Abdominoperineal resection of the rectum with regional lymph node dissection (D3) was carried out. The resected specimen showed a 27×35×15mm blackish protruding tumor with dark pigmentation and a blackish gray spot in the surrounding mucosa. Microscopical features were as follows: mp, ly0, v0, ow (-), aw (-), n0, stage 1. Adjuvant chemotherapy was not performed. He has been well for 14 months after operation without any evidence of tumor recurrence. Although the treatment of choice for malignant melanoma is controversial because of the extremely poor prognosis, only radical excision was effective in this case. Histological findings, which revealed that melanoma cells existed in a gray spot separate from the main protruding lesion, suggest that careful observation of the surrounding mucosa and adequate surgical treatment with enough margin are important.
