Introduction

The incident round cancer detection rate is increasing. We have reviewed the imaging characteristics of these cancers at diagnosis and, if present, on the previous screening round to document their imaging progression.

Methods

Over a 10-year period, 844 incident round cancers presented through the South East London Breast Screening Programme. Screening mammograms were reviewed from the incident and previous screening round. Age, mammographic and histological size, mammographic sign, tumour type, grade and nodal status at diagnosis were documented. When visible previously, mammographic size and sign, position in breast and interpretation were noted.

Results

Twenty-six percent (216 of 844) of incident round cancers were potentially detectable on the previous screening mammograms (group 1). Of these, 69% were interpreted as subtle/uncertain and 29% as suspicious with the majority in the 'milky way' (55%). Seventy-four percent (628 of 844) were not visible previously (group 2). The most frequent mammographic sign at diagnosis was a spiculated mass (group 1, 56%; group 2, 48%; P = 0.0025). If present previously (group 1), the most likely signs were a mass (57%) (P = 0.001), micro-calcification (13%) or an asymmetric density (10%). There was a significant difference in mammographic size between the cancers at diagnosis (mean 17 mm) and on the previous round (mean 10 mm) (P = 0.01). Most tumours were grade 2 at diagnosis (group 1, 46%; group 2, 45%). In group 1 there were significantly more grade 1 tumours (43%) and nearly half the amount of grade 3 tumours (11%) (P = 0.0001).

Conclusion

If visible on previous mammograms, incident round cancers are likely to be small, of low grade and appear as a mass, asymmetric density or focus of microcalcification.