A case of anorectal malignant melanoma in which narrow-band imaging was used to observe local recurrence 9 years after surgical resection

An 80-year-old woman was admitted to our hospital for the work-up of bloody stool. Colonoscopy showed a protruding brownish lesion of 15-mm diameter in her rectum. Furthermore, narrow-band imaging (NBI) showed regular and partial-pitting structures with abnormal corkscrew vessels on the surface of the lesion. We suspected a malignant melanoma on the basis of the above endoscopic findings. The lesion was treated by endoscopic mucosal resection; it was pathologically diagnosed as a malignant melanoma. Nine years earlier, she had been treated by local excision for an anorectal malignant melanoma. However, the resection was incomplete because the vertical margin of the biopsy was positive for tumor cells. Additional surgery had not been performed as follow-up at the request of the patient and her family. Therefore, we considered this lesion to be a recurrence. The 5-year survival rate of anorectal malignant melanoma was reported to be 5.2%. This is the first reported case in which NBI was used to observe an anorectal malignant melanoma in a patient who experienced long-term survival.