Pathological observation on fibromatosis of breast

Objective:To observe the clinicopathological features,immunohistochemical type and differential diagnosis of fibromatosis of breast. Methods: One case of mammary fibromatosis was studied with histopathology,immunohistochemistry examination and involved literatures review. Results: Grossly,the mass was nodulated and indistinct margin,with a firmly and white-grey cut surface. Microscopy revealed that the neoplasm was composed of spindle cell and collagen fibers,arrayed bunchy and striation,extended to lobule-tube structure of periphery mammary as finger,and infiltrated into fat. Lymphocytic infiltration was seen in the lesions and most prominent at the margins. Immunohistochemical findings showed that the tumor cells were positive for vimentin and SMA,partly positive for actin and desmin,but negative for ER,PR,AE1/AE3,CK5/6,EMA,CD34 and S-100 protein,though Ki-67 5%. Conclusion: Fibromatosis is a rare benign soft tumor of the breast,consisting of proliferating fibroblast cells,myofibroblast cells and collagen fibers. It is usually indistinguishable from carcinoma in physical examination,mammography and ultrasound. The diagnosis mainly relies on hitopathological sections. Morphologically,it should be differentiated from other spindle cell lesions in the breast,such as fibromatosis-like spindle cell carcinoma,myoepithelial carcinoma,myofibroblastoma,fibrosarcoma,nodular fasciitis and reactive spindle cell nodules.