# A 21-Year-Old Female with Invasive Breast Cancer within a Benign Phyllodes Tumor

## TL;DR

A 21-year-old woman was diagnosed with invasive breast cancer within a benign phyllodes tumor, a rare condition difficult to detect preoperatively.

## Contribution

This case report highlights the rare occurrence of breast cancer within a phyllodes tumor in a very young patient.

## Key findings

- A 21-year-old female was diagnosed with invasive ductal carcinoma within a benign phyllodes tumor.
- Preoperative imaging and biopsy could not reliably predict the presence of cancer due to the patient's age and lesion characteristics.
- The case underscores the importance of thorough pathological examination in complex breast masses.

## Abstract

Although breast cancer occurring within a phyllodes tumor (PT) has been reported, it is extremely rare in young patients. Herein, we describe a case of breast cancer complicated by a PT in a 21-year-old female.

A 21-year-old female was referred to our hospital with a rapidly growing breast mass and suspected PT. Mammography revealed a well-defined, high-density mass. Ultrasonography revealed a blood-flow-rich hypoechoic mass with multiple slit structures, and MRI revealed a heterogeneous high signal on T2 weighted image with some diffusion restriction. A core needle biopsy revealed fibroepithelial lesions, and the lack of stromal changes suggested a high possibility of fibroadenoma. Based on the clinical and imaging findings, we considered the possibility of the PT being more than borderline malignant and planned tumor resection with a safety margin. The postoperative pathology revealed a benign PT complicated by invasive ductal carcinoma, with a predominance of intraductal carcinoma.

We report the case of a 21-year-old female with breast cancer occurring within a PT. The presence of cancer was difficult to predict preoperatively based on the patient’s young age and imaging findings.