Screen-detected malignant breast lesions diagnosed following benign (B2) or normal (B1) needle core biopsy diagnoses.

UNLABELLED: Breast needle core biopsy (NCB) is now a standard diagnostic procedure in the triple assessment of screen detected breast lesions. However, unlike fine needle aspiration (FNA) cytology, information on the miss rate including false-negative diagnoses (FN) of malignancy (benign 'B2' or normal 'B1' NCB with a malignant outcome) is limited. METHODS: A large series of NCBs (121,742) performed over an 8-year period has been studied to assess the frequency and causes of missing a malignant diagnosis on NCB and to evaluate their impact on patients' management in the screening service. RESULTS: During the period of this study, 50,691 were diagnosed as B2 and 9599 were diagnosed as B1. Of those, 779 B2 and 919 B1 were diagnosed as malignant on the subsequent surgical specimens, respectively, giving a FN rate of 3.0%. However when year of diagnosis was taken into consideration, we found that during the period 1999-2001, the FN rate for B2 was 2.7% while the miss rate for B1 was 4.0%. This showed marked improvement over time to reach a figure of 0.5% and 0.5% for B2 and B1, respectively, during the period 2005-2007. On detailed review of cases from a single screening region diagnosed during the last 3 years (2005-2008), 14 cases (0.17% of all NCBs) with malignant surgery were diagnosed as B2 (seven cases; FN rate 0.19%) and B1 (seven cases; B1 biopsy rate from cancer 0.19%). In these cases, NCB was unsatisfactory, there was a discrepancy between radiological abnormalities and histological findings with recommendation for excision or suspicious/malignant cytological diagnosis on concurrent FNA material. Therefore, our results indicate that the malignancy miss rate on NCB is rare and FN NCB diagnoses had no impact on patient management.

Screen-detected breast lesions with malignant needle core biopsy diagnoses and no malignancy identified in subsequent surgical excision specimens (potential false-positive diagnosis).

Although breast needle core biopsy (NCB) is now a standard diagnostic procedure in the triple assessment of screen-detected breast lesions, data on the false-positive diagnoses of malignancy (malignant NCB 'B5' with normal/benign surgery) are lacking. In this study, we have studied a large series of NCBs (101,440) to assess the causes and pitfalls resulting in false-positive NCB diagnoses and to evaluate their impact on patients' management in the screening service. Our results showed that of 40,395 malignant NCBs reported during the period of this study, 174 NCBs are considered as false-positives (0.43%; (95% confidence interval [CI]=0.37-0.49%)). However, on review, 165 cases (95%) were found to be the result of true removal of the whole lesion in the core with subsequent negative excision biopsy samples (true-positive NCBs). This may reflect sampling of small screen detected lesions and the use of larger core biopsies at assessment. The remaining 9 cases were considered as true false-positive cores, giving a false-positive rate of 0.02% (95% CI=0.01-0.04%). Analysis of these 9 cases showed that 8 cases, originally diagnosed as DCIS, were classified as borderline lesions or lesions of uncertain malignant potential after surgical excision. The classification and management of such borderline lesions remains controversial and diagnostic surgical excision is usually the optimum management. One case was the result of pathological misinterpretation of fat necrosis as invasive carcinoma. This was the only case that resulted in a significant over-management of the patient. In conclusion, our results showed that the true false-positive rate of NCB is extremely rare. Significant over-management of screen-detected breast lesions as a result of false-positive NCB may be considered almost nil.

Audit of performance of needle core biopsy diagnoses of screen detected breast lesions.

Breast needle core biopsy (NCB) is now a standard diagnostic procedure in the triple assessment of screen detected breast lesions. Therefore, it is important to provide robust and up-to-date data on the performance of NCB in the screening setting. However, previous studies of NCB have suffered from either limitation in the number of assessed cases or included a mix of symptomatic and screen detected breast lesions. In this study, we have evaluated the performance of a large series of uniformly assessed NCBs of screen detected lesions (20001 cases) over a period of 10 years (1997-2007). Our results showed a gradual increase in the number of NCBs and an improvement of their performance over the period of the study; absolute sensitivity increased from 84.9% to 96.4% and complete sensitivity increased from 90.9% to 99.7%. There was also a gradual reduction in the number of surgical interventions after benign (B2) and negative (B1) NCB diagnoses. Our study provides data showing variance from the suggested thresholds for the measures of performance of NCB in the United Kingdom which could be used to provide updated evidence-based thresholds for assessment of performance of NCB diagnosis use in the assessment of breast cancer screen detected lesions in the UK and elsewhere.