Immunohistochemical study of fibroblast activation protein and α-smooth muscle actin expression and distribution in triple-negative breast cancer

Introduction:Triple negative breast cancer constituting 10-20% of all breast cancers, and are more frequently in younger patients with poor prognostic outcome , The tumor microenvironment is formed of activated fibroblasts which known as Cancer associated fibroblasts, which can be detected by fibroblast activation protein [FAP] and α-smooth muscle actin [α-SMA].Aim of the work: evaluation of the expression and distribution of FAP and α-SMA in triple negative breast cancer.Material and methods: this study was carried on 100 paraffin blocks from pathologically proved triple negative invasive breast cancer patients and subjected to immunostaining of SMA and FAP antibodies, Evaluation of antibodies expression according to its distribution in tumor margin and in tumor center.Results: There were significant differences between FAP as well as SMA expression in tumor center and tumor margin, FAP and SMA expression in the tumor center was positively correlated with tumor size and grade.In contrast to tumor margin FAP and SMA expression was negative correlated with tumor size and lymph node metastasis. Conclusion:We speculated that high FAP expression and α-SMA expression in the tumor center, but not the tumor margin, is correlated with poor patient's clinicopathological parameter.