[A Case of Metachronal Phyllodes Tumors That Presented Bilaterally in the Breast].

A 33-year-old woman underwent resection of a right breast mass, which was diagnosed as a fibroadenoma 15 years ago. Ten years later, a right breast mass appeared again, and it was diagnosed as a fibroadenoma based on core needle biopsy. After observation for a while, the mass increased in size, and she underwent resection of the tumor, which was diagnosed as a borderline-malignant phyllodes tumor. A mass appeared again in the right breast and rapidly expanded. A malignant phyllodes tumor was suspected, and right mastectomy was performed. The pathological diagnosis revealed a benign phyllodes tumor. Four years ago, a left breast mass was also detected. Because the mass was suspected to be a fibroadenoma, it has been observed for a few years. The mass has increased in size since 1 year ago, and another mass emerged 2 months ago. Core needle biopsy of the 2 masses revealed that both were phyllodes tumors. She underwent left mastectomy, and the pathological examination revealed that both masses were benign phyllodes tumors. We report this rare case of metachronal phyllodes tumors that presented bilaterally.