CA 15.3, or Mucin 1, cell surface associated, is a human gene encoded by MUC1. It may also be known as: Mucin-1; MUC-1; Breast carcinoma-associated antigen DF3; Cancer antigen 15-3; CA 15-3; Carcinoma-associated mucin; Episialin; H23AG; Krebs von den Lungen-6; KL-6; Peanut-reactive urinary mucin; Polymorphic epithelial mucin; PEM; Tumor-associated epithelial membrane antigen; Tumor-associated mucin; CD antigen CD227; ADMCKD; ADMCKD1; CD227; MAM6; MCKD; MCKD1; MUC-1/SEC; MUC-1/X; MUC1/ZD. The encoded protein has an amino acid length of 1255 and a mass of 122.1 kDa. Homologs of this gene exist in other organisms, including: Mouse.