Phyllodes tumour

Definition

• Rare biphasic fibroepithelial tumour of the breast with a morphological continuum from benign to malignant, accounting for 0.3–1% of primary breast tumours.

Classification

• The WHO distinguishes benign, borderline and malignant tumours by nuclear atypia, stromal cellularity, mitoses, tumour margin and stromal overgrowth; 60–75% are benign.
• Benign tumours have fewer than 5 mitoses per 10 HPF, borderline tumours 5–9 and malignant tumours 10 or more.

Occurrence & epidemiology

Epidemiology

• Mainly women aged 40 to 50 years are affected; benign forms tend to occur at a younger age than borderline and malignant tumours.

Clinical features

• Through rapid growth the tumour can bulge the breast, stretch the skin and ulcerate; dilated skin veins and nipple changes occur.
• Enlarged axillary lymph nodes are relatively common and usually reactive, whereas nodal metastases are very rare.

Histology

• Histology shows a hypercellular stroma with an increased intracanalicular growth pattern and leaf-like structures, lined by a double layer of epithelium, projecting into cystic spaces.

Diagnosis

• Mammography usually shows well-defined, dense masses; ultrasound shows a solid hypoechoic mass, usually with posterior acoustic enhancement and often increased vascularity on Doppler, cystic areas being more typical of malignant forms.
• Distinction from fibroadenoma is difficult, especially on core biopsy; imaging alone cannot reliably distinguish benign from malignant forms.

Keep learning in the app

Further reading (selection)

1. StatPearls: Phyllodes Tumor of the Breast (NCBI Bookshelf)
2. Phyllodes tumors of the breast: a comprehensive review of diagnosis … (Clinics 2025, PubMed Central)

Cross-references