Experimental study on histological origin of breast phyllodes tumor

Objective To observe the pathologic characteristics of breast phyllodes tumor and discuss the histological origin of malignant stroma.Methods Thirty cases of paraffin blocks of phyllodes tumor were collected and clinical material of the patients were reviewed. The expression of vimentin,cytokeratin,desmin and actin were immuohistochemically detected.And the ultrastructure of phyllodes tumor was studied by electroscope in 2 cases of phyllodes tumor.Results No expression of cytokeratin and desmin were found in all of the 30 cases, and positive expressions of vimentin were found in all of the 30 cases. The positive expressions of actin were different in the 30 cases of phyllodes tumor (6 cases strong positive, 5 cases positive, 10 cases weak positive, and 9 cases negative).Conclusion Neoplastic cells of phyllodes tumor are probably derived from periductal fibroblast and it can differentiate to smooth muscle and myofibroblast.