Pseudoangiomatous stromal hyperplasia. A benign proliferation of fibroblasts and myofibroblasts with numerous intersecting slit-like spaces in a densely hyalinised stroma, which simulates a low-grade angiosarcoma.
The remaining lesions included fibroadenomas, hemangioma, duct ectasia, pseudoangiomatous stromal hyperplasia, fat necrosis, and intramammary lymph nodes.
Interestingly, one-fourth of all the benign biopsies had columnar cell lesions, alone or associated with pseudoangiomatous stromal hyperplasia or other proliferative changes such as usual ductal hyperplasia.
Pseudoangiomatous stromal hyperplasia is a benign proliferative lesion composed of anastomosing empty, slitlike pseudovascular spaces lined by myofibroblasts that resemble endothelial cells set in a dense collagenous stroma.
10) Similarly, pseudoangiomatous stromal hyperplasia (PASH), which represents the other end of the spectrum of the myofibroblastic lesions, also exhibits foci of increased cellularity with a fascicular arrangement of myofibroblasts resembling the bland spindle cell metaplastic carcinoma.