Expression of MLH1, MSH2 in Malignant Melanoma

Kim, Young Jin; Kim, Min Gwan; Lee, Yoon Se; Choi, Seung Ho; Kim, Sang Yoon; Nam, Soon Yuhl; Huh, Ju Ryung

Abstract

BACKGROUND AND OBJECTIVES
MLH1 and MSH2, which are DNA mismatched repair genes, used to be studied in HNPCC (hereditary nonpolyposis colon cancer). Now, the defects in MLH1 and MSH2 are known to be related with malignant transformations of other tumor. Mismatched repair proteins are widely dispersed in the adnexal structures. According to studies, if mismatched repair proteins were stained, as melanocytic nevi progresses into melanocytic dysplastic nevi and cutaneous malignant melanoma, positive immunoreactivity decreases. The purpose of the study is to find out the appearance pattern of DNA mismatched repair proteins, and MLH1 and MSH2 known to be associated with microsatellite instability and carcinogenesis. MATERIALS AND METHODS: Of 19 patients who had been diagnosed with malignant melanoma by pathological study in Asan medical center between June, 1989 and January, 2002, 11 patients had mucosal malignant melanoma while 8 patients had malignant melanoma on the skin. There were 9 males and 10 females, with the average age of 55 (32-77). We investigated the nuclear positivity of MLH1 and MSH2 by immunochemical staining of paraffin tissue method. RESULTS: The nuclear positivity of MLH1 and MSH2 were 27.3% (3/11) and 36.8% (7/11), respectively, indicating that there were no significant differences. Three cases of 4 metastatic mucosal malignant melanoma cases showed negative MLH1 response and MSH2 had 2 positive and 2 negative responses. Biopsy after metastasis represented negative conversion of nuclear activity in MLH1 in only on case, and this indicated a loss of activity as the disease progressed. Four except one of the metastatic cutaneous malignant melanoma cases showed negative staining of MLH1 and MSH2. CONCLUSION: We found decreased nuclear activity in MLH1 and MSH2 in the cutaneous malignant melanoma and mucosal malignant melanoma. This information can be applied for diagnosis or follow-up methods of malignancy in the future.