Cytological Criteria to Distinguish Phyllodes Tumour of the Breast from Fibroadenoma.

OBJECTIVE: To determine whether there are significant differences between fibroadenomas and phyllodes tumours with regard to selected cytomorphological features. STUDY DESIGN: A 10-year retrospective review was performed of patients who underwent excision of a fibroadenoma or phyllodes tumour and in whom a preoperative fine-needle aspiration was performed. The following cytological criteria were assessed: number of stromal and epithelial fragments, stromal-to-epithelial ratio, stromal cellularity, stromal borders, stromal atypia, and proportion of background wavy spindled cells. Patient age, tumour laterality, and tumour size were recorded. RESULTS: Fifty fibroadenomas and 17 phyllodes tumours were included. Compared to phyllodes tumours, fibroadenomas had a larger number of epithelial fragments, a smaller number of stromal fragments, and a lower stromal-to-epithelial ratio. The stroma tended to be less cellular and less atypical compared to phyllodes tumours and the background cellular population contained fewer spindled cells. CONCLUSION: Fibroadenomas and phyllodes tumours differ with regard to various cytological features, aiding in their distinction on fine-needle aspiration biopsy.