Breast phyllodes tumors (PTs) are uncommon tumors with a biphasic fibroepithelial component, characterized by rapid development in middle-aged women. A correct preoperative diagnosis after Tru-Cut biopsy allows for proper surgical planning. The treatment of choice remains surgery (wide local excision or mastectomy) with or without breast reconstruction, depending on the size and histopathological (HP) nature of the tumor. We reported a case of a 50-year-old woman with a large PT in her left breast, measuring 11∕10 cm. Preoperative HP examination revealed biphasic proliferation, with the appearance of benign PT. The patient underwent a left mastectomy, with a favorable postoperative evolution. The final HP diagnosis was borderline PT, with areas of lipomatous metaplasia. After three months, breast reconstruction was performed. The therapeutic management of large PTs continues to be a challenge for pathologists and surgeons. Due to the increased frequency of local recurrence and HP progression to malignancies, the treatment of choice for these patients is mastectomy, without lymphadenectomy.