Pseudoangiomatous Stromal Hyperplasia of the Breast

Abstract

Pseudoangiomatous stromal hyperplasia of the breast is a benign stromal lesion that can be mistaken as fibroadenoma on clinical and ultrasonographic examination or as a low grade angiosarcoma on histological examination. Pseudoangiomatous stromal hyperplasia may be seen incidentally in about 23% of breast biopsies. Although exact etiology and pathogenesis of pseudoangiomatous stromal hyperplasia is still unknown, reactivity of myofibroblasts against endogeneous hormones particularly progesterone is thought to be responsible. Because mass forming lesions are rare we present a case of pseudoangiomatous stromal hyperplasia which was diagnosed as fibroadenoma on clinical and ultrasonographic examination. A 27year-old woman presented with a right breast mass. After physical and ultrasonographic examination, it was diagnosed as fibroadenoma and excision was done. Histopathological examination revealed a lesion composed of complex anastomosing vessel-like slits in a dense collageneous stroma. These slits were outlined by endothelial-like spindle cells. These spindle cells were negative for CD31 while CD34 and SMA were positive. Reactivity with CD34 and SMA showed myofibroblastic differantiation of spindle cells. Although unclear, aberrant reactivity of myofibroblasts against progesterone is suggested in pathogenesis of pseudoangiomatous stromal hyperplasia. Unlike the previous reported cases, the negativity of myofibroblastic cells for progesterone in our case suggest other factors aside from progesterone may play role in the etiology.