MCAT and breast carcinoma: The transgenic mice FVB/N-Tg (MMTV-PyVT) 634Mul/J (transgenic mice PyVT) express the oncogene of Middle T Antigen (MT), which induces the transformation of cells from mammary tissue to a tumorigenic state; thus, the mice have a predisposition to developing breast cancer (Guy, Cardiff & Muller, 1992).