6. Audit of breast screening core biopsy diagnostic performance measures at pathwest fiona stanley hospital (FSH) from 2015 to 2016

Abstract

Background: Core needle biopsy (CNB) is widely utilised in the investigation of screen detected breast abnormalities. National and international guidelines recommend classification of biopsies into categories: ‘non-diagnostic (B1)’, ‘benign (B2)’, ‘atypical/indeterminate (B3)’, ‘suspicious (B4)’ and ‘malignant (B5)’, each with common diagnostic and therapeutic implications. Accurate classification is imperative to reduce morbidity associated with breast screening programs such as over-diagnosis and the resulting overtreatment of patients. This issue is particularly relevant to the ‘indeterminate/atypical (B3)’ and ‘suspicious (B4)’ lesions on core biopsy where further tissue is required specifically for the purpose of diagnostic clarification and not treatment per se. Aims: To assess the performance of Fiona Stanley Hospital (FSH) PathWest category reporting of screening breast core biopsies over a 2-year period against UK National Health Service (NHS) standards. Methods: Retrospective collection of data regarding the diagnostic category classification of all breast core biopsies reported at PathWest FSH in the period between January 2015 and December 2016. Results and conclusions: Out of 2470 breast lesions examined in this audit, 3.2% were non-diagnostic, 55.7% benign, 6.1% atypical, 0.4% suspicious and 34.5% malignant. The rate of B3 and B4 lesions in this audit were well within the NHS audit expected targets. The other categories were also comparable to rates found in similar large international studies. These results, a component of the pathology quality assurance metrics of a breast screening program, are a surrogate for adequate application of diagnostic criteria to all diagnostic categories, but are particularly relevant to the atypical/indeterminate category where there is great potential for over-investigation.