Large tumoral pseudoangiomatous stromal hyperplasia with ER/PR stromal negativity in a 20-year-old female: A rare case report.

Pseudoangiomatous stromal hyperplasia (PASH) is a rare lesion of the breast stromal tissue with unknown mechanism. Hormonal stimulation of mammary myofibroblasts is the most important theory due to stromal positivity of progesterone receptor (PR) or/and estrogen receptor (ER). We report a case of PASH with stromal PR/ER negativity.