Clinical case giant malignant phyllodes tumor of the breast.

Malignant phyllodes tumor is a rare and aggressive breast neoplasm with the potential for rapid and recurrent growth. We present the case of a 56-year-old woman from San Martín, Peru, with a left breast mass exhibiting exponential growth, ulceration, necrosis, and asymmetry. Physical examination revealed a multinodular, purplish-red, indurated, and slightly painful mass. Ultrasound showed a 12-cm hypoechoic, heterogeneous mass with areas of necrosis, increased vascularity, and contact with the muscle layer (Breast Imaging Reporting and Data System category 4). Core biopsy revealed a fibroepithelial neoplasm with high mitotic activity (10/10 HPF). The patient underwent left total mastectomy with subsequent margin extension and partial-thickness skin grafting, achieving complete resection and satisfactory recovery. This case highlights the challenges in the diagnosis and surgical management of this pathology in resource-limited settings where timely surgery plays a crucial role in treatment and prevents recurrence.