Nodule-Forming Pseudoangiomatous Stromal Hyperplasia of the Breast: Report of Three Cases.

Pseudoangiomatous stromal hyperplasia (PASH) is a benign proliferative entity of mammary stroma. It is generally found as an incidental finding. It may rarely present as a palpable nodule. Three patients, who were 29, 45, and 58 years of age, were referred to our clinic with nodule and pain in the breast. The physical examinations and ultrasound findings of all three patients were consistent with fibroadenoma. Core biopsies were performed and reported as "benign breast parenchyma including stromal fibrosis." PASH areas were noted in one case. The excision specimens were observed as solid nodular masses with smooth external surfaces and white in colour. Microscopically, well-demarcated hyalinized stroma, including slit-like pseudovascular spaces lined by bland spindle cells, was observed. Immunohistochemically, these cells showed positive staining for CD34 and negative staining for CD31. Nodule-forming PASH mostly confuses with fibroadenoma with respect to clinical examination and radiological findings. Definite diagnosis requires histopathological verification. Differential diagnosis should be made with low grade angiosarcoma, fibroepithelial tumors, and myofibroblastoma.