Periductal Stromal Hyperplasia and Periductal Stromal Tumor

Periductal stromal tumors (PDST), originally defined by Burga & Tavassoli, are marked by cuffs of spindled, mitotically active stroma encasing open lobules. This group presents a classification challenge. PDST are composed of two entities, the rarer initial presentation of periductal stromal hyperplasia (PDSH) and the more common presentation of periductal stromal sarcoma (PDSS). PDST are uncommon biphasic breast lesions that occur in perimenopausal and postmenopausal women (range: 24–89-years-old). PDST represent <1% of breast malignancies. Previously thought to be a subcategory of phyllodes tumors, their status as a distinct entity remains unclear.