Pseudoangiomatous stromal hyperplasia (PASH) is a benign lesion composed of a stromal proliferation of myofibroblasts. Microscopically the appearance is of a hyalinized collagenous stroma with anastomosing slit-like pseudovascular spaces lined by spindle cells. By immunohistochemistry, it is negative for endothelial cell markers such as ERG, CD34, and CD31.