Catenins are proteins that are linked to the cytoplasmic domain of transmembrane cadherins. p120 Catenin is a member of this Armadillo gene family of junctional plaque proteins. The association of catenins to cadherins produces a complex which is linked to the actin filament network, and which seems to be important for cadherins cell-adhesion properties. Cytoplasmic accumulation of p120 Catenin has been observed in lung cancer, pancreatic cancer, gastric cancer and colon cancers and is associated with poor progress in colon cancer patients. In breast lobular neoplasia, p120 Catenin shows a diffuse cytoplasmic immunostaining pattern, while breast ductal neoplasia retains the membrane immunostaining pattern. p120 Catenin is useful in differentiation of lobular carcinoma from ductal carcinoma of the breast and in identifying early lesions of lobular neoplasia.