Implication of MT1-MMP in the maturation steps of benign melanocytic nevi

Background: Metalloproteinases (MMPs) are proteins involved in extracellular matrix breakdown and have been implicated in stages of migration and metastasis. MT1-MMP is an MMP anchored to the cell membrane. During maturation, melanocytic nevi penetrate the extracellular matrix and express MMPs. Methods: We studied 10 junctional, 10 compound, and 10 intradermal nevi diagnosed by clinical and histological studies and by performing immunohistochemical study to assess MT1-MMP activity. Results: We found evidence of MT1-MMP expression in melanocytic nevus cells, particularly around the entire border of cell nests. Expression was more intense in junctional nevi and gradually decreased with acquisition of intradermal component and became nonexistent in nevi in the deep dermis. Conclusions: MT1-MMP is expressed in the membrane of nevus cells, with expression greater in nest cells in contact with the extracellular matrix. The intensity of expression correlated inversely with the maturation phase of the nevus, being very high in junctional nevi and low in intradermal nevi.