Phyllodes tumour among participants in screening mammography.

Background: In screening, the distinction between phyllodes tumour (PT) and fibroadenoma (FA) is imprecise, often needing surgery.

Methods: In this retrospective cohort study and literature review, we wished to (i) present our experience with PT diagnosed among screening participants; (ii) identify discriminating features between FA and PT; (iii) assess the efficacy of cancer screening in identifying PT; and (iv) for women diagnosed with PT, determine appropriate breast cancer screening schedules.

Results: During a 23.7 years time frame, PT was diagnosed in 30 women, reflecting an incidence of 2.53 per 100 000 women screened. Only 22 (73.3%) PT were found by screening. The remaining eight (26.7%) presented as interval tumours. Thirteen PT were benign, eight borderline and nine malignant. Six of eight (75%) malignant PT were symptomatic. A circumscribed mass, mean diameter 34.7 mm, was the dominant finding. Enlargement (14 imaging, seven clinical) was documented in 21 (70%) cases. Diagnostic open biopsy was required in 67.9%. Follow-up of at least 12 months is available in 20 cases. Only two developed recurrence. One woman died of metastatic PT and one PT recurred locally.

Conclusion: The extreme rarity of PT in screening contrasts with the prevalence of FAs. The peak incidence of PT in women is 40-50, whereas screening is targeted at women 50-74. Two yearly screening mammography is not designed to detect PT reliably. In particular, malignant PT grows rapidly and becomes symptomatic. Women with benign PT can continue with screening. Women with borderline and malignant PT should resume screening after 5 years of specialist surveillance.