MAMMOGRAPHIC AND PATHOLOGICAL FEATURES OF BREAST-CANCER DETECTED AT FIRST INCIDENT ROUND SCREENING

This study investigated the proportion of first incident screen detect ed cancers diagnosable at prevalent round. The prevalent mammogram was classified as truly negative (no abnormality) or falsely negative (ca ncer diagnosable) after blinded review. Of 54 incident cancers, 63% we re true and 26% false negatives. Five cancers were assessed at the pre valent round but dismissed as normal. The possible consequence of dela yed diagnosis was inferred from the pathological prognostic indicators and calculated Nottingham prognostic index of the incident rumours, a nd comparison with prevalent screen, symptomatic and interval cancers. Compared to the true negatives, a significantly greater proportion of false negative incident tumours were in the very good prognostic grou p, i.e. in many of the latter the prognosis is probably unaffected, al though in part this is because a number of the fast growing false nega tive tumours will result in interval cancers. Significantly fewer inci dent tumours were of good prognosis compared to the prevalent round, p ossibly an adverse affect of 3-yearly screening. Parenchymal deformiti es and calcifications were the most frequent false negative mammograph y signs and appear to represent good prognosis lesions.