Aims: The UK National Health Service Breast Screening Programme has proposed five categories for reporting breast needle core biopsies. The majority of cores are reported as benign (B1), normal (B2) or malignant (B5). The predictive value of the two borderline categories suspicious of malignancy (B4) and lesion of uncertain malignant potential (B3) was studied.
Methods and results: Over a 2-year period a total of 3822 breast needle core biopsies were performed, with 2997 from symptomatic patients and 825 from women undergoing mammographic screening, including 43 B4 reports (40 patients) and 120 B3 reports (116 lesions in 115 patients). The frequencies of B4 (2.5% versus 0.7%) and B3 cores (7.3% versus 2.0%) were both higher in screening than in symptomatic patients. B4 was most commonly used for small fragments of atypical cells separate from the main core or focal atypical intraductal proliferations. The criteria for calling a core B3 were: atypical intraductal epithelial proliferations (including foci that in excision specimens would be classified as atypical ductal hyperplasia), lobular neoplasia, radial scar, papillary lesion, fibroepithelial lesion with cellular stroma and spindle cell proliferations. Excision biopsies were performed in 39 patients with B4 core and 96 with B3 core. Invasive carcinoma or ductal carcinoma in situ was seen in 33 of the patients with B4 (85%) and in 29 of those with B3 cores (25%). Some categories of B3 core were associated with a higher rate of malignancy (40% for atypical intraductal epithelial proliferations and 46% for lobular neoplasia).
Conclusions: The positive predictive value for carcinoma is high following a B4 core (86%). The lesion should be excised, but definitive cancer treatment is not appropriate. In some cases a definite diagnosis of malignancy can be made on repeat core. The B3 group is more heterogeneous and has a lower rate of malignancy on further biopsy (25%). The majority of B3 lesions require excision. All these patients should be discussed at multidisciplinary meetings.