Tumor-stromal interactions in breast tumor progression--significance of histological heterogeneity of tumor-stromal fibroblasts.

INTRODUCTION: Existing pathological diagnostic protocols for breast cancer do not fully reflect the biological characteristics of tumor stromata. To improve the pathological diagnosis of breast cancer, a new pathological diagnostic method capable of assessing the degree of breast cancer malignancy based on the histological features of the tumor stroma is needed. AREAS COVERED: The presence of a fibrotic focus (FF), which consists of fibroblasts or collagen fibers, and the presence of atypical tumor-stromal fibroblasts are significantly associated with nodal metastasis or distant-organ metastasis in patients with invasive ductal carcinoma (IDC) of the breast. FF is the only factor that is significantly associated with an increase in tumor angiogenesis. The importance of FF and atypical tumor-stromal fibroblasts clearly indicates that the malignant potential of IDC does not depend only on the biological characteristics of the tumor cell, but also on those of the tumor stroma. EXPERT OPINION: The biological characteristics of fibroblasts forming an FF or atypical tumor-stromal fibroblasts probably differ from those of fibroblasts located outside an FF or ordinary tumor-stromal fibroblasts. Thus, similar to tumor cells, the heterogeneity of tumor-stromal fibroblasts probably influences the outcome of patients with IDC of the breast.