Breast fibroadenoma with pseudoangiomatous (PASH-like) stroma.

Pseudoangiomatous stromal hyperplasia (PASH) is a breast stromal change, histologically characterized by anastomosing, slit-like spaces lined by slender myofibroblasts and surrounded by dense collagenous stroma. Mass forming cases clinically and radiologically simulate fibroadenoma. A middle aged women presented with unpalpable breast nodule discovered on ultrasound examination. The ultrasound characteristics were typical for fibroadenoma, while fine-needle aspiration cytology was inconclusive. The histological examination of the lumpectomy specimen showed fibroadenoma with peculiar stromal alteration consistent with pseudoangiomatous stromal hyperplasia. The presented case of fibroadenoma with pseudoangiomatous hyperplasia within its stroma demonstrates the relationship between these two entities not only clinically and radiologically, but also histologically.