Ductal carcinoma in situ arising within a benign phyllodes tumour is a rare neoplasm of the breast. We present a case of a 19-year-old woman who had a right breast lump for six months with the above diagnosis together with a mini-review of the literature. Ultrasound revealed a 5-cm breast lump and core biopsy revealed ductal carcinoma in situ. She underwent wide local excision of the breast lump with clear margins. Final histology confirmed ductal carcinoma in situ within a fibroepithelial lesion consistent with a benign phyllodes tumour. To our knowledge, this is the youngest case of ductal carcinoma in situ arising in a phyllodes tumour to have been reported so far.