Expressional Difference of RHEB, HDAC1, and WEE1 Proteins in the Stromal Tumors of the Breast and Their Significance in Tumorigenesis

BACKGROUND Fibroadenoma (FA) and phyllodes tumor (PT) are stromal tumors of breast and are histologically similar. There are no established differences in tumorigenesis and oncogene expression among them. Ras homolog enriched in brain (RHEB) plays an important role in cell growth and cell-cycle control, histone deacetylase 1 (HDAC1) is an important factor in breast tumor progression and prognosis, and WEE1 homolog (WEE1) functions as a tumor suppressor. No studies on the expressional differences of these proteins in FA and PT have been reported to date. METHODS The expression of these proteins in FA, PT, and normal breast was compared. We used 102 cases of FA and 25 cases of benign PT. RESULTS In epithelial cells, the expression of RHEB, HDAC1, and WEE1 was lowest in PT, higher in FA, and most enhanced in normal breast. In addition, the expression of RHEB and HDAC1 was higher in the stromal cells of PT than in FA and normal breast. CONCLUSIONS Both epithelial and stromal cells of FA and PT express these proteins, which indicates that epithelial cells play an important role in the development of stromal tumors. In addition, the expressional differences of these proteins may be associated with the tumorigenesis of breast stromal tumors.