Case report: rapid growth of malignant phyllodes tumor.

Phyllodes tumors (PT) are exceedingly rare fibroepithelial neoplasms that arise from breast stromal tissue, primarily occurring in women in the fourth and fifth decade. This poses a diagnostic challenge among younger women with breast masses, such as those in their late teens to early thirties, where benign breast masses such as fibroadenomas are more common. In this report, a 19-year-old female presented with a rapidly enlarging complex mass of the right breast over the course of two months. An ultrasound revealed a mass measuring 19 × 17 × 23 cm, with multiple solid and cystic components. The mass was classified as BI-RADS 4. Due to the continuous growth, the patient underwent total right mastectomy. Final pathology revealed a malignant phyllodes tumor measuring 24 × 12 × 7 cm with cystic component. Phyllodes tumor management remains complex, requiring a tailored multidisciplinary approach based on individual tumor characteristics and patient factors.