FGFR2 and invasive breast carcinoma: Thus, breast cancer progression may involve two distinct alternative splicing events, first involving the expression of FGFR2 IIIb C2/C3 isoforms associated with progression from normal breast epithelium to noninvasive breast cancer, and secondly involving the conversion to the mesenchymal FGFR2 IIIc isoform in invasive breast cancer cells [55].