Breast fibroblastoma without smooth muscle differentiation

Abstract

Background/Aim: To report a very rare case of breast fibroblastoma without smooth muscle differentiation. Case report: A 42-year-old women presented left breast tumor of non-nipple location, and core needle biopsy (CNB) was diagnosed as benign phillodes tumor by the author. The tumor was solid white and measured 23 mm × 31 mm × 33 mm. Microscopically, a thick capsule was noted, and the tumor was composed of a proliferation of mesenchymal spindle cells; no epithelial element was seen. Frequently, tumor cells shows striform or cartwheel appearances. No significant mitotic figures were seen. Immunohistochemical study showed that the tumor cells were positive for vimentin, CD10, CD68, estrogen receptor, and progesterone receptor. The p53 was negative and Ki-67 labeling index was < 1%. The tumor cells were negative for cytokeratin (CK) AE1/3, CK CAM5.2, CK34BE12, CK7, CK20, h-caldesmone, alpha-smooth muscle actin (ASMA), desmin, myoglobin, S100 protein, KIT, CD34, CD45, synaptophysin, Factor VIII-related antigen, CD31, CEA, and EMA. The pathological diagnosis was fibroblastoma of breast. Conclusion: A very rare case of breast fibroblastoma without smooth muscle differentiation is reported.