ABSTRACT
Phyllodes tumors are an infrequent breast tumor presentation. A phyllodes tumor with a synchronous invasive ductal carcinoma is rarely described and has never been reported with lobular carcinoma in situ component. A 53-year-old female presented with a nine-year history of twice core biopsy proven fibroadenoma. After an increase in the tumor's growth velocity it was decided upon to undergo an excisional biopsy. Microscopic examination of the well-circumscribed pale-tan mass found focal areas of leaf like architecture with variable number of mitoses present, representing a phyllodes tumor of borderline malignant potential. Incidentally, at one edge of the mass was found a tubular carcinoma and lobular carcinoma in situ components. Thorough, routine follow-up of patients with biopsy proven benign breast masses is important to finding a masked malignant component.