Ductal carcinoma in situ arising in a benign phyllodes tumor: report of a case.

Malignant epithelial change within a phyllodes tumor (PT) is a rare event. To our knowledge, only six cases of ductal carcinoma in situ arising in a PT have been reported in English. We report a case of PT with an intraductal carcinoma component, which grew rapidly to a huge size in 3 months. Histologically, the stromal element showed mild to moderate cellularity with few mitoses and mild nuclear atypia. The epithelial element consisted of irregularly dilated ducts with a phyllodes structure that had moderate to severe epithelial hyperplasia, and foci of cribriform ductal carcinoma in situ with comedo necrosis.