Phyllodes tumor (PT) is an uncommon fibroepithelial tumor of female breast.  Ductal carcinoma in situ (DCIS) in the epithelial component of PT is very rare.

 We report a rare case of DCIS arising in a benign PT in a 48–year–old lady. The patient presented with a lump in left breast, noticed 20 days back. Ultrasonography failed to distinguish between fibroadenoma and PT. A tumor measuring 5.6×3.6×3.2 cm was removed by local excision. Histological examination revealed foci of DCIS within the benign Phyllodes tumor, without any invasive component. While coexistent carcinoma and cystosarcoma phyllodes in the same breast have been reported, it’s rare for the carcinoma to develop within the cystosarcoma phyllodes.

Our case highlights the importance of assessing phyllodes tumors for concurrent in situ and invasive carcinoma involvement, as this may affect both the need for axillary lymph node examination and subsequent treatment options.