Significance of Basic Fibroblast Growth Factor and Fibroblast Growth Factor Receptor Protein Expression in the Formation of Fibrotic Focus in Invasive Ductal Carcinoma of the Breast

A fibrotic focus (FF) is a scar‐like area within invasive dnctal carcinoma (IDC) of the breast, and has been shown to be a marker of high aggressiveness of IDC. In order to investigate the mechanism of FF formation in IDC, expression of basic fibroblast growth factor (bFGF) and flbroblast growth factor receptor (FGFR) was studied. One hundred and forty‐nine IDCs were divided into solid tumors and scirrhous tumors. Immunohistochemistry was used to determine the expression of bFGF and FGFR proteins in both tumor cells and fibroblasts forming FF. Scirrhous tumors with FF showed a significantly higher frequency of bFGF protein expression than those without (P=0.017), whereas, in solid tumors, the presence of FF was not significantly associated with the frequency of bFGF protein expression (P=0.143). In addition, scirrhous tumors showed a significantly higher frequency of FGFR protein expression than solid tumors (P=0.001). Among IDCs having FF and expressing bFGF protein, a significantly larger number of fibroblasts expressing FGFR protein within FF was observed in scirrhous tumors than in solid tumors (P=0.016). The results of this study suggest that in scirrhous tumors the interaction between tumor cells and stromal fibroblasts plays an important role in the formation of FF, and that there is a paracrine mechanism between bFGF protein from tumor cells and FGFR protein in fibroblasts.