Abstract
OBJECTIVE: Anorectal malignant melanoma (AMM) is frequently subjected to misdiagnosis. Here the effect of misdiagnosis on the prognosis of AMM was investigated. METHODS: Between 1995 and 2007, 79 patients managed for AMM were reviewed; 46 (58.23%) of them had been misdiagnosed during the symptoms, while 33 (41.77%) cases had been diagnosed exactly not more than 1 week after the first visit. Diseases misdiagnosed were categorized as cancer, hemorrhoids, polyps and other diseases. Data were statistically analyzed by using the life tables and Kaplan-Meier curves. The software used was SPSS 16.0 for Windows. RESULTS: The 1-, 2-, 3- and 5-year survival rates of AMM patients were 58, 33, 24 and 16%, respectively, and the median survival time was 14.0 months; 1-, 2-, 3- and 5-year survival rates of the misdiagnosed patients were 61, 22, 22 and 11%, respectively, and the median survival time was 14.0 months; 1-, 2-, 3- and 5-year survival rates of the patients not misdiagnosed were 55, 44, 25 and 25%, respectively, and the median survival time was 12.0 months. Analyses based on Kaplan-Meier curves revealed no significant effect of misdiagnosis on the survival of AMM patients (P > 0.05). Nevertheless, the diseases misdiagnosed significantly affect the prognosis (P = 0.009); AMM misdiagnosed as hemorrhoids had a poor prognosis, with a 1-year survival rate of only 29% and the median survival of only 6.0 months. CONCLUSIONS: The misdiagnosed patients had relatively poor prognosis, but the effect of misdiagnosis on the prognosis was not significant; however, misdiagnosis of AMM as hemorrhoids seriously affected the prognosis.