Recurrent Fibroadenoma and Concomitant Mucinous Cancer with Ductal Carcinoma In situ Following Benign Phyllodes Tumor Excision: A Rare Case Report.

A 37-year-old woman was diagnosed with a fibroadenoma (FA) with concomitant extensive spreading of ductal carcinoma in situ (DCIS) and multifocal mucinous carcinomas in 2022. Previously, she was first diagnosed with a FA and received excision in 2016. The initial clinical presentation was a palpable mass in the left breast. During periodic breast ultrasound examination in 2020, another newly developed tumor was found in the same region. A core biopsy revealed a fibroepithelial lesion. The patient received wide excision surgery. The final pathology report indicated a phyllodes tumor (PT) with a clear margin. All three events occurred in the same region (left breast, at 2 O'clock and 3-5 cm from the nipple). Our patient had a relapsed FA, which progressed into a benign PT and FA concomitant with DCIS and multifocal mucinous carcinomas. We report this case to highlight the need for continuous follow-up for FA cases even after complete resection and the possibility of recurrence with other fibroepithelial tumors.