Low-grade uterine endometrioid adenocarcinomas (EACs) may exhibit a distinct pattern of myometrial invasion characterized by the presence of microcystic, elongated, and fragmented ('MELF') glands but the factors influencing this pattern of invasion are not known. Immunohistological expression of CD147 (extracellular inducer of matrix metalloproteinase, EMMPRIN) and matrix metalloproteinase-2 (MMP2) was studied in 22 EAC and the results compared between the 'conventional' neoplastic glands, foci of MELF-type invasion, and in the tumor-associated stroma. The conventional tumor areas showed strong membranous expression of CD147, and staining was more consistently present toward the central (luminal) aspect of the larger glands. In contrast, the tumor cells showed only focal expression of MMP2, and in some cases CD147 and MMP2 staining was inversely correlated. The neoplastic epithelium within MELF areas usually was negative for both CD147 and MMP2. However, there was consistent MMP2 expression in the reactive stroma that characteristically surrounds foci of MELF pattern invasion. This micro-anatomical variation in protein expression within EAC suggests a functional alteration in the neoplastic epithelium during the invasive process. It is likely that stromal MMP2 plays a role in potentiating invasion in these tumors but this may be regulated by factors other than CD147.
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