Expression of adhesion molecules and epithelial-mesenchymal transition factors in medullary carcinoma of the colorectum.

Medullary carcinoma (MC) of the colorectum is known as a rare variant with favorable prognosis despite its poorly differentiated morphology. The mechanism of its favorable behavior has been unclear. Here, we compared the expressions of adhesion molecules and epithelial-mesenchymal transition (EMT)-related proteins in the central portion and invasive front between 43 MCs and 30 poorly differentiated adenocarcinomas (PDAs). The expressions of membranous E-cadherin (P < .0001), β-catenin (P < .0001) and claudin 1 (P = .0036) were significantly preserved in the invasive front of the MCs compared to those in the invasive front of the PDAs. E-cadherin membranous expression was also significantly preserved in the central portion of the MCs (P = .0178). Nuclear β-catenin expression in both the central portion (P = .0463) and invasive front (P = .0346) of the MCs was significantly less frequent compared to that in the PDAs. Snail (P = .0035) and Twist1 (P = .0463) expressions in the invasive front of the MCs were significantly less frequent compared to the PDAs, suggesting that the EMT phenomenon may occur rarely in colorectal MC. Reduced membranous E-cadherin expression in the MC central portion was significantly correlated with poor clinical outcome (P = .0086). Our immunohistochemical results indicate that preserved adhesion molecule protein and less frequent expression of EMT-related transcription factors in the invasive front contribute to the favorable prognosis of colorectal MCs. We suggest that a reduced expression of E-cadherin in the central portion might be a good biomarker for an unfavorable prognosis in cases of MC.