1994 Volume 44 Pages 136-138
A 56-year-old male visited a hospital in his neighborhood with the complaint of anal bleeding. At that hospital, he was diagnosed as anorectal malignant melanoma on the basis of colonoscopic biopsy. Then he was admitted.
Barium enema and colonoscopy demonstrated two elevated lesions contacting each other, and having irregular surface. The lesions, however, did not show black, the typical deature of melanoma. The pathological diagnosis of resected specimen was“hypomelanotic malignant melanoma”.
In case of malignant melanoma, it is adbocated that to perform biopsy is contraindicated because it may promote metastasis. But, as in this case, it is very difficult to diagnose amelanotic or hypomelanotic malignant melanoma precisely by colonoscopy. We must distinguish anorectal malignant melanoma from rectal carcinoma so that we may choose different therapy for them as the case may be. At present, we should depend on biopsy to make differential diagnosis between them.
