Beta-Catenin

The catenins are structurally related cytoplasmic proteins which have been classified as alpha (α), beta (β), and gamma (γ), these proteins can bind to the highly conserved, intracellular cytoplasmic tail of E-cadherin. Together, the catenin/cadherin complexes play an important role mediating cellular adhesion. β -catenin associates with the cytoplasmic portion of E cadherin, which is necessary for the function of E-cadherin as an adhesion molecule. β -catenin has also been found in complexes with the tumor suppressor protein APC. In normal tissues, β -catenin is localized to the membrane of epithelial cells, consistent with its role in the cell adhesion complex. In breast ductal neoplasia, β-catenin is usually localized in cellular membranes. However, in lobular neoplasia, a marked redistribution of β-catenin throughout the cytoplasm results in a diffuse cytoplasmic pattern. Immunostaining of β -catenin and E-cadherin is helps in the accurate identification of ductal and lobular neoplasms, including a distinction between low-grade ductal carcinoma in situ (DCIS) and lobular carcinoma. Additionally, some rectal and gastric adenocarcinomas demonstrate diffuse cytoplasmic β-catenin staining and a lack of membranous staining, mimicking the staining pattern observed with lobular breast carcinomas.