Immunohistochemical expression of matrix metalloproteinase-2 (MMP-2) in common melanocytic nevi, dysplastic nevi and primary cutaneous malignant melanomas

MMPs play a significant role in the progression of different types of human tumors as well as malignant melanomas. MMP-2, which is also known as 72-kD type IV collagenase is a member of MMPs. The aim of this immunohistochemical study is to evaluate the role of MMP-2 expression in common melanocytic nevi, dysplastic nevi and primary cutaneous malignant melanomas. Formalin-fixed paraffin-embedded materials from 21 common melanocytic nevi (CMN), 42 dysplastic nevi (DN) and 18 primary cutaneous malignant melanomas (MM) were examined. Standard streptavidin-biotin immunoperoxidase method was used for immunostaining with MMP2 antibody. Both tumoral and stromal cytoplasmic MMP2 expressions in melanocytic lesions were scored semiquantitatively. MMP-2 immunoreactivity was not observed in stromal and/or melanocytic cells in either common melanocytic or dysplastic nevi. Eleven of 18 malignant melanomas expressed MMP-2. Five cases showed positive cytoplasmic staining only in stromal cells, and six cases in both stromal and melanocytic cells. MMP-2 was more commonly expressed at the tumor-stroma interface where significant amount of plasma cells and lymphocytes were observed. MMP-2 expression does not appear to be related to the pathobiology of benign melanocytic lesions such as common melanocytic nevi and dysplastic nevi. On the other hand, MMP-2 expression by the cells in the tumor stroma, particularly by endothelial cells and fibroblasts, may play a significant role in melanoma pathobiology.