Crude open biopsy rates for benign screen detected lesions no longer reflect breast screening quality--time to change the standard.

Objectives: To investigate the changing nature of the benign screen detected breast abnormalities removed at open biopsy over a seven year period and to compare this with the improving cancer detection rate and non-operative diagnosis rate.

Setting: The Bolton, Bury, and Rochdale Breast Screening Programme.

Methods: The histopathology reports of the benign lesions removed from patients undergoing open biopsy for screen detected abnormalities between 1 April 1994 and 31 March 2001 were reviewed and the lesions classified on the B1 to B5 scale. Cancer detection rates and non-operative cancer diagnosis rates were ascertained from the breast screening computer system.

Results: 148 benign surgical biopsies were performed in the seven year period. There was a moderate increase in the overall benign biopsy rate over the period (from 1.26 open biopsies per 1000 women screened for the three years 1994-97 to 1.63 open biopsies per 1000 women screened for the three years 1998-2001). The biopsy rate for B2 (benign) lesions decreased slightly over the study period but the biopsy rate for B3 lesions (that is, of uncertain malignant potential) more than doubled. The majority (84%) of the B3 lesions were radial scars. There was a steady improvement in the cancer detection rate and the non-operative cancer diagnosis rate over the period, similar to that seen nationally.

Conclusions: Improvements in screening technique and detection ability result in an increase in the number of subtle radiologically indeterminate or suspicious lesions detected. Many of these are radial scars, which require excision. Crude benign open biopsy rates for screening programmes are no longer meaningful, and should now be refined with separate rates for B2 lesions and B3 lesions. High quality programmes can expect to have low B2 open biopsy rates and high B3 open biopsy rates. It is inappropriate to have an upper limit for the B3 open biopsy rate.