Abstract: The patient had an 8-year history of breast mass showing rapid growth to 15cm×13cm within 1 year.Imaging suggested BI-RADS 4B cystic-solid mass,with postoperative pathology confirming borderline phyllodes tumor（PT） (14cm×13cm×8cm) showing ER/PR(-) and Ki-67 15%.Literature review indicates PT accounts for <1% of breast tumors,with core needle biopsy outperforming fine-needle aspiration.Surgical excision remains primary treatment,yet optimal margin width is debated .This case highlights the necessity of considering PT for rapidly growing breast masses and advocates triple assessment for accurate diagnosis.

Key words: breast; borderline phyllodes tumor; case report