20 Te success of reproduction relies primarily on the ability of the developing embryo to establish an intimate connection with its mother, through a process of embryonic attachment and implantation that allows the embryo to penetrate deeply into the maternal decidua and to invade the endometrial spiral arteries [1]. A series of synchronized and strictly regulated molecular and biochemical interactions are required for suc- cessful implantation, including degradation and remodeling of the extracellular matrix by various enzymes [2]. Te fact that trophoblastic cells from first trimester exhibit behaviors similar to these of cancer cells, such as migration and invasion, is re- ally impressive. Although placental trophoblastic cells behave like metastatic cancer cells, they are only transiently invasive. Specifically, their invasion is limited to the first trimester and spatially to the endometrium and the proximal third of the myometrium [1]. Te invasive phenotype of placental cells has been directly linked to their ability to produce extracellular matrix metalloproteinases (MMPs) [3]. Te MMPs are a family of more than twenty proteases that can virtually process all extracellular matrix components [4–6]. Teir proteolytic activity allows them to participate in many steps of tumor progression such as involvement in the early stages of tumor growth and development, alteration of cell adhesion , degradation of basic membranes-extracellular matrix and angiogenesis [7]. MMP2 and MMP9 (also known as gelatinases) were initially viewed only as essential proteases for basal membrane-invasive events , but the finding that MMP2 is also produced by mesen- chymal cells and MMP9 by inflammatory cells (macrophages and neutrophils) at the tumor site has attributed to them the Comparative study of the immunohistochemical expression of metalloproteinases 2, 7 and 9 between clearly invasive carcinomas and “in situ” trophoblast invasion I. IOANNIDIS 1 , B. DIMO 1 , A. KARAMERIS 1 , G. VILARAS 1 , H. GAKIOPOULOU 2 , E. PATSOURIS 2 , A. C. LAZARIS 2 1 Department of Pathology, 417 N.I.M.T.S Hospital, Athens, Greece; 2 1st Department of Pathology, School of Medicine, National and Kapodistrian University of Athens, Greece. Email: ycioannidis@gmail.com Received March 5, 2009 Matrix metalloproteinases (MMPs) are endopeptidases considered to participate in the transient invasive property of trophoblastic cells during embryo implantation and placentation. Te same molecules play an important role in the invasive and metastatic potential of cancer cells. Te aim of this study was to compare the immunohistochemical expression of MMP2, 7 and 9 between clearly invasive carcinomas and “in situ” trophoblast invasion in an effort to illuminate their distinct roles in uncontrolled and controlled invasion. We performed an immunohistochemical analysis of 45 clearly invasive carcinomas of various organs (colorectal, gastric, breast, pulmonary, renal) and 40 first trimester gestation specimens (before the 9 th week of gestation). Te markers expres- sion was evaluated semiquantitavely, seperately in cancer parenchymal and gestational trophoblastic cells as well as cancer stromal and decidual cells, according to a percentage scale (0 %, <10%, 10-50% and >50% of cells) and according to staining intensity (0, +, ++, +++). MMP9 was expressed more ofen in the malignant parenchymal as well as in the malignant stromal component of car- cinomas than in the trophoblastic (p=0, 0118) and decidual (p=0,017) component of gestations respectively. Although all carcinomas and almost all gestation specimens stained for MMP2 and MMP7, the immunostaining for both molecules was statistically more extensive and intense in trophoblasts and decidual cells by comparison to cancerous elements. In conclusion, although there seems to be a direct link between cancer invasion and MMP9 immunohistochemical expression, the role of MMP2 and MMP7 appears to be more complicated underlining the complexity of the mechanisms involved in cancer spreading. Key words: metalloproteinases, invasive carcinomas, trophoblast invasion Neoplasma 57, 1, 2010 doi:10.4149/neo_2010_01_020