Research and analysis

National breast screening pathology audit

Updated 21 September 2021

Applies to England

1. Executive summary

1.1 Overview

This National Breast Screening Pathology Audit has been produced for the 3-year period April 2016 to March 2019. The report aims to inform pathologists of the range in performance across screening service/laboratory biopsy quality assurance (BQA) statistics, to allow assessment of laboratory pathology performance against relevant standards and to facilitate comparison of departmental results with other services.

Pathology outcomes for non-operative reporting were obtained from the national breast screening system (NBSS) system. BQA reports have been generated for the most significant non-operative biopsy result (known as client level), rather than at individual pathologist level in this report (a total of 118,223 biopsies).

The charts in this report are based on data from the accompanying data tables spreadsheet. To enlarge any of the charts, you can zoom your browser window by pressing [Ctrl]+ or open the chart in a new browser tab.

1.2 Summary of important findings

Low volume laboratories

A total of 46 (35%) laboratories were excluded from the analysis due to reporting low numbers of biopsies (less than 30 in this 3-year period). This represented a total of only 286 biopsies being excluded (0.2%) in total. Further investigation by the Screening Quality Assurance Service (SQAS) of the use of these laboratories is warranted.

B3 with/without atypia

The reporting of associated atypia in B3 lesions has not previously been audited in the national pathology audit. It is mandatory for all B3 core biopsy results to record whether there is, or is not, associated epithelial atypia and the nature of that atypia. There is wide variation across services and it is unlikely that the marked differences observed reflect actual differences in pathology practice. Data entry is felt to be the most likely cause of this variation.

It is recommended that communication between pathologists and all staff entering data into NBSS be improved to facilitate accurate recording of this data field. Pathologists should ensure clarity in core biopsy reports and any unit that is an outlier in this measure should consider performing an audit of data accuracy.

B3 PPV variation

There is very wide variation in the percentage of total B3 results that are malignant on a surgical specimen. A low threshold for reporting biopsies as B3 will result in a high B3 rate and potentially a subsequent increased benign biopsy rate and a low positive predictive value (PPV) for B3.

It is recommended that services that are low outliers should triangulate this information with overall use/percentage of the B3 category and with benign biopsy rates. It may also be worthwhile confirming that vacuum-assisted excision (VAE) procedures for B3 lesions have been correctly identified and coded, which may result in no real or apparent further diagnostic intervention following a B3 result.

High outliers for PPV B3 should examine the number, and type, of needle biopsies undertaken at assessment, as adequate diagnostic work-up in the first instance may have prevented an unnecessary diagnostic (rather than therapeutic) surgical specimen with malignant histology.

PPV B3 with/without atypia

The recording of the presence or absence of atypia in B3 lesions has not previously been audited in the national pathology audit.

The accuracy of recording these data fields will clearly influence the PPV of B3 lesions with and without atypia. It is recommended that any unit that is an outlier in this measure should consider performing an audit of data accuracy.

False positive rate

A potential false positive is any case with a B5 core biopsy followed by a normal or benign surgery. The current BQA downloads show inaccurate false positive rates due to the way NBSS analyses data for those cases where cancers have been removed on core biopsies or where there has been complete pathological response following neoadjuvant therapy. In addition, some clients are not correctly allocated on NBSS. Out of 100 false positive cases shown on the BQA report, just 10 are considered accurate.

1.3 Discussion

This report presents an opportunity for breast screening pathologists to examine their laboratories’ results and to identify and address variation in practice. In some instances, it is recognised that a significant contributing factor to variation is data quality. This may be challenging for pathologists to tackle due to the complexities around who performs data entry in different services. However, it is important to address these problems to ensure that true variation in clinical practice can be correctly identified in the future.

It must also be remembered that the performance presented in this audit is not purely reflective of the pathologists’ adherence to reporting of specimens in line with national guidance. The data are multi-factorial and some elements are outside the control of the pathology department. For example, the accuracy of the operator to sample the index lesion, the radiological threshold for sampling, and the availability and use of vacuum assisted techniques significantly impact many parameters. Sharing of the results with breast screening colleagues, particularly radiologists, may be valuable.

2. Aims and objectives

This report aims to inform pathologists of the range in performance at the screening service/laboratory level of BQA (non-operative biopsy) statistics and to allow assessment of their laboratories’ pathology performance against standards indicated in Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening^{[footnote 1]}, and to facilitate comparison of their departmental results with those of other services.

3. Data sources

The NBSS system is used by all 78 screening services in England to record outcomes of women invited for screening. This includes information at all stages in the pathway through screening: attendance, assessment and treatment. Pathology outcomes for non-operative reporting are obtained from the NBSS system. BQA reports have been generated for the most significant non-operative biopsy result (known as client level), rather than at individual pathologist level in this report (a total of 118,223 biopsies for the 3-year period from April 2016 to March 2019) and are presented here.

3.1 Exclusions

Control chart analyses are shown in the document with 95% control limits and 99.7% control limits.

Hospital laboratories with 30 or more biopsies over the 3-year period only are included in the performance charts (99.5% of all core biopsies, n=117,596 with 627 biopsies excluded in total). This number is derived from a total of 117,959 biopsies from 78 English breast screening services, as the aggregated hospital laboratory totals from each breast screening service may include more biopsies due to a different pathologist reporting the same lesion. Of the 627 exclusions, 341 had an unknown laboratory of origin and the remaining 286 were excluded for analysis due to reporting low numbers.

It is surprising that 35% of laboratories in England reported less than 30 breast screening core biopsies in this 3-year period. This amounts to approximately 10 per annum, representing only 0.2% of all biopsies reported. With the mean average being 6.2 biopsies per smaller laboratory. The skewness of these data is demonstrated by the median average number of biopsies for the smaller laboratories being just 2.0. Results for smaller laboratories tend towards extreme values, making interpretation difficult and the predominant reason for excluding small volume laboratories is that analysis of units with such small numbers indicates that their inclusion would not provide meaningful results.

Further investigation into the use of these laboratories would seem warranted. It is advised that SQAS should explore both the accuracy of the data and explanations for the low numbers.

Whilst NHSBSP Pathology Quality Assurance guidance recommends that a breast screening pathologist should report a minimum of 50 primary breast cancer resection specimens each year^{[footnote 2]}, there are no specific guidelines regarding the minimum number of breast screening core or vacuum-assisted biopsy cases a pathologist should report. However, if an individual reports limited numbers of non-operative specimens per year, they should consider whether they are receiving sufficient exposure to maintain expertise; this is particularly true if all consultants in a department between them report less than 30 cases in a 3-year period.

Data tables are provided in the companion spreadsheet which show overall numbers of cases for the 3-year period by breast screening service. The Breast Screening Service (BSS) code is used as the unique identifier for each hospital laboratory within regions.

4. Reporting categories

Histological examination of core biopsy samples is reported using the classifications B1 to B5. For more detailed definitions, see Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening (June 2016). The definitions of each classification are given below.

B1 (normal tissue)

This indicates a core of normal tissue whether or not breast glandular structures are present, thus this category is equally appropriate for a core including normal breast ducts and lobules or mature adipose tissue or stroma only.

B2 (benign)

A core is classified as B2 benign when it contains a benign abnormality. This category is appropriate for a range of benign lesions including fibroadenomas, fibrocystic change, sclerosing adenosis and duct ectasia and extends to include other non-parenchymal lesions such as abscesses and fat necrosis.

B3 (lesion of uncertain malignant potential)

This category mainly consists of lesions that may provide benign histology on core biopsy, but either are known to show heterogeneity or to have an increased risk of associated malignancy.

B4 (suspicious of malignancy)

Technical problems such as crushed or poorly fixed cores that contain probable carcinoma but cannot provide the definitive diagnosis are best included as B4. Similarly, small groups of apparently neoplastic cells contained within blood clot or adherent to the outer aspect of the sample should be classified as B4 – suspicious. Very small foci suspicious of invasive carcinoma in which there is insufficient material to allow immunocytochemical studies may also reasonably be assigned to this category.

B5 (B5a non-invasive, B5b invasive, B5c invasive status unknown)

This category is appropriate for cases of unequivocal malignancy on core biopsy. B5 category is further subdivided into B5a, B5b and B5c. B5a should be classified for unequivocal ductal carcinoma in situ (DCIS) of all grades and pleomorphic lobular carcinoma in situ (LCIS), the report stating whether the lesion is DCIS or LCIS (classical lobular neoplasia is categorised as B3). B5b is used for all invasive primary breast carcinomas and rare invasive malignancies including malignant phyllodes, lymphomas and metastatic tumours. B5c is used when it is not possible to say whether the carcinoma is invasive or in situ.

5. Performance measures – targets

Minimum and achievable standards are from ‘Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening’ (June 2016)^{[footnote 3]}.

Performance measure	Minimum (%)	Preferred (%)
Absolute sensitivity	> 92	> 95
Complete sensitivity	> 99	> 99.5
Specificity (biopsy cases only)	-	-
Specificity (full)	> 75	> 85
Positive predictive value B5	> 99.5	> 99.9
Positive predictive value B4	-	-
Positive predictive value B3	-	-
Negative predictive value B2	-	-
False negative rate (B2 from cancer)	<0.5	< 0.2
False positive rate	< 0.2	< 0.1
B3 rate	4 to 9	4.5 to 8.5
B4 rate	< 1.5	< 1
Miss rate (B1 + B2) from cancer	<5	<1

6. Performance

6.1 Number of WBN reported (clients)

The total number of wide bore needle (WBN) biopsies included in this report (2016 to 2019) is 117,959. The range of biopsies reported by a hospital laboratory (n <30 excluded) is 32 to 4,159.

Bar chart showing proportion of core biopsies by reporting category by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.2 Proportion of total WBN results reported as B1 to B5

Bar chart showing proportion of core biopsies by reporting category by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

6.3 Proportion of core biopsies reported by category in England

(Overall B5: 46.0%, B4: 0.6%, B3: 7.9%, B2: 41.3%, B1: 4.3%).

The proportion of total WBN results that are reported as B1 to B5 will be dependent on a variety of factors, including the population case mix, the accuracy of the operator to target the appropriate area of suspicion, the degree of specificity of the operator, the threshold for biopsy of lesions at assessment and the accuracy of the pathologist in classifying specimens according to the Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening (June 2016).

6.4 B1 rate (clients)

Identifiers shown for 99.7% upper outliers. Plotted against England average of 4.3%

Funnel plot showing B1 rate by number of WBN results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.5 B2 rate (clients)

Identifiers shown for 99.7% upper outliers. Plotted against England average of 41.3%

Funnel plot showing B2 rate by number of WBN results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

Interpretation

Outliers for B1 or B2 rates (or both) should assess the proportion of B1 to B3 outcomes in comparison to the national average. An audit of a sample of B1 and B2 lesions should be undertaken to ensure that reporting complies with national guidance and to ensure that the B1 category, normal, is not applied when B2, benign, would be more appropriate or vice versa.

High outliers for B1 core biopsy rates may be attributable to a low threshold for performing needle core biopsies; it is therefore advisable to examine the proportion of women undergoing needle core biopsy tests at the service in comparison to the national average (see below). The proportion of women referred for core biopsies/cytology are shown in the following graphs for each breast screening service in England. These data may help to triangulate the relationship with radiology.

The PPV of referral for assessment at the unit is defined as the number of cancers expressed as a proportion of all women referred for assessment. This should also be examined to establish whether there is a tendency to biopsy lesions with a very low suspicion of malignancy mammographically. It is also sensible to examine the miss rate (B1+B2) from cancers (below). This may be higher than expected which suggests mis-targeting of the lesion by the operator.

The following graph shows the proportion of clients biopsied and diagnosed with cancer per 100 clients assessed during the screening period 1 April 2016 to 31 March 2019. England averages a biopsy rate of 46.1% and cancer detection rate of 21.7%.

Bar chart showing the proportion of clients biopsied and diagnosed with cancer per 100 clients assessed by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

The following graph shows the proportion of clients assessed, biopsied and diagnosed with cancer per 1,000 clients screened during the period 1 April 2016 to 31 March 2019. England averages an assessment rate of 39.3, biopsy rate of 18.1, and a cancer detection rate of 8.5.

Bar chart showing the proportion of clients assessed, biopsied and diagnosed with cancer per 1,000 clients screened by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

6.6 Negative predictive value (NPV) B2 (client)

The number of lesions that are not cancer identified as B2 expressed as a percentage of the total number of B2 results. England NPV 99.9 (median 100%). Hospital laboratory range: 98.8% to 100%.

6.7 False negative rate (B2 from cancer) (clients)

Number of false negative results expressed as a percentage of the total number of carcinomas sampled. NHSBSP standard: <0.5% (minimum), <0.2% (achievable). England false negative rate 0.07%. Hospital laboratory range: 0% to 0.76% (n. 3/394).

Interpretation

This indicator measures the percentage of all cancers on surgical histology which obtained a B2 result non-operatively. This indicator is closely related to the negative predictive value, as the numerator is the number of malignancies categorised as B2 non-operatively.

Low outlier status represents optimal performance, by the operator for accurately targeting the lesion or the pathologist for correctly recognising and diagnosing benignity.

6.8 Core biopsy miss rate (B1 and B2 from cancer) (clients)

Number of cancers with prior core biopsies that were categorized as B1 or B2. NHSBSP standard: <5% (minimum), <1% (preferred). England core biopsy missed rate 0.10%. Hospital laboratory range: 0% to 0.76% (3/394).

Interpretation

It is clearly good practise that a review at a multi-disciplinary team (MDT) meeting is undertaken at services for any cancers which had a B1 outcome reported non-operatively. Although it is conceivable that the diagnosis was missed by the pathologist who reported the core as B1, the target lesion reported by the film reader may not have been sampled. Hence, the reasons and justifications for not repeating the core should be examined.

6.9 Specificity (biopsy cases only) (clients)

The NHSBSP measures full specificity for all benign lesions (including those without final histology) and specificity for biopsy cases only. Services with high specificity for biopsy cases only effectively mean that a high proportion of cases which were proven benign at open biopsy had a B2 reporting outcome non-operatively. England specificity: 6.6%

Bar chart showing specificity (biopsy cases only) for all benign lesions by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Identifiers shown for lower and upper 99.7% outliers. Plotted against England average of 6.6%

Funnel plot showing specificity (biopsy cases only) for all benign lesions by total number of benign lesions by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Interpretation

Being a high outlier for this measure could be due to greater use of the B2 reporting category with possible underuse of the B3 category. Services with high specificity (biopsy only) are often outliers for reporting in the B2 and/or B3 categories. If B3 is seldom used, the MDT meeting decision could be influencing the decision to refer the woman to surgical excision biopsy. The availability of VAB may be influential in this measure.

6.10 Full specificity (clients)

Number of correctly identified benign lesions (the number of B2 results minus the false negatives) expressed as a percentage of the total number of benign lesions biopsied.

NHSBSP standard: >75% (minimum), >85% (achievable). England specificity: 77.9% (median 78.9%)

Bar chart showing full specificity for all benign lesions by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Identifiers shown for 99.7% lower outliers. Plotted against England average of 77.9%

Funnel plot showing full specificity for all benign lesions by total number of benign lesions by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Interpretation

Full specificity is likely to be high with accurate identification of benignity and for this reason, services whose performance demonstrate high outlier status is not problematic. Low outliers should examine the B1 core biopsy rate, as this may be high, and could indicate either sub-optimal or mis-sampling by the operator, although conversely this may represent a low threshold for sampling by the radiologist or advanced practitioner.

The proportion of women assessed undergoing needle tests should be compared to other units and the national average (see earlier) and the PPV of referral (the number of cancers expressed as a proportion of all women referred from screening for assessment) examined, as this may indicate if a low threshold for sampling is a contributory factor. If the PPV of referral is low, this may be due to radiological aspects of performance.

However, variation in the way pathologists report cases as B1 or B2 may be significant, especially when histological changes are minor or there is discordance with history. The Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening (June 2016) has clear guidance on how B1 and B2 should be reported, for example recommending that minor changes such as mild fibrocystic change should be classified as B1 and not B2.

Services which have a low rate of specificity may also have a rate of benign biopsy outside the QA minimum standard of <1.5 per 1000 screened. It is worth assessing the benign biopsy rate in conjunction with specificity, as high rates may indicate an overuse of the B3 reporting category in these circumstances.

6.11 B3 rate (clients)

NHSBSP standard: minimum 4% to 9%; preferred 4.5% to 8.5%. England B3 rate 7.9%

Bar chart showing B3 rate by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

Identifiers shown for 99.7% lower and upper outliers. Plotted against England average of 7.9%

Funnel plot showing B3 rate by number of WBN results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.12 B3 with and without atypia (clients)

It is mandatory for all B3 core biopsy results to record whether there is, or is not, associated epithelial atypia and the nature of that atypia (ductal, lobular or flat epithelial atypia). Across England there were no cases where the presence or absence of atypia was not reported. The proportion of B3 biopsies in England with atypia is 52.7% and without atypia is 47.3%.

Bar chart showing proportion of B3 biopsy results with or without atypia by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

B3 with atypia identifiers shown for lower and upper 99.7% outliers. Plotted against England average of 52.7.0%.

Funnel plot showing proportion of B3 biopsy results with atypia by total number of B3 results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

B3 without atypia identifiers are shown for lower and upper 99.7% outliers. Plotted against England average of 47.3%

Funnel plot showing proportion of B3 biopsy results without atypia by total number of B3 results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Interpretation

The reporting of associated atypia in B3 lesions has not previously been included in the national pathology audit and it is apparent that there is wide variation. Although there are no cases in this time period England where the presence or absence of atypia has not been recorded it is regarded as unlikely that the marked differences between units reflect pathology practice but rather data entry.

It is recommended that communication between pathologists and all staff entering data into NBSS be improved to facilitate accurate recording of this data field and in particular that pathologists should ensure clarity in core biopsy reports. Any unit that is an outlier in this measure should consider performing an audit of data accuracy.

6.13 Final histology of B3 with atypia

England biopsies reported as B3 with atypia but with no further histology (no surgery or VAE), 51.4%. Range from 6.5% (n. 4/62) at LPL to 100% at (n. 10) at CBA.

England reported final histology of B3 lesions with atypia that were benign is 35.3%, 11.8% non-invasive and 1.6% invasive.

Bar chart showing final histology of B3 lesions with atypia by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

6.14 Final histology of B3 without atypia

England biopsies reported as B3 without atypia and no further histology (no surgery or VAE); 52.1%. Range from 0% (n. 14) at DSW to 100% at (n. 17) at CRO.

England reported final histology of B3 lesions without atypia that were benign 42.3%, non-invasive 4.6% and 1.0% invasive.

Bar chart showing final histology of B3 lesions without atypia by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Interpretation

Both B3 lesions with and without atypia recorded appear not to have further investigation in a high proportion of cases (51.4% with atypia and 52.1% without atypia). This seems unlikely in view of recommended clinical management and may reflect misuse of the appropriate forms on NBSS which now exist for vacuum-assisted excision specimens. For example, the data may be completed as for vacuum-assisted biopsy rather than excision.

It is essential that pathologists are informed as to the nature of a vacuum-assisted specimen (either biopsy or excision) and that they subsequently facilitate accurate entry of data to NBSS.

6.15 PPV B3 (clients)

This indicator measures the percentage of total B3 results which are malignant on a surgical specimen. England PPV B3: 9.7% (median 9.3%)

Bar chart showing the proportion of total B3 results which are malignant on a surgical specimen by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Identifiers shown for 99.7% lower and upper outliers. Plotted against England average of 9.7%

Funnel plot showing the proportion of total B3 results which are malignant on a subsequent surgical specimen by total number of B3 results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Interpretation

There is very wide variation, in the rate of B3 diagnosis and in the PPV of B3 between services.

Low outliers should triangulate this information with overall use/percentage of the B3 category and with benign biopsy rates. A low threshold for reporting biopsies as B3 will result in a high B3 rate and potentially a subsequent increased benign biopsy rate and a low PPV for B3. It may be worthwhile confirming that vacuum-assisted excision (VAE) procedures for B3 lesions have been correctly identified and coded. This may result in no real or apparent further diagnostic intervention following a B3 result, for example, if incorrectly labelled/defined as ‘biopsy’ and thus given a B code on data entry.

High outliers for PPV B3 should examine the number, and type, of non-operative biopsies (core needle biopsy or vacuum-assisted biopsy) undertaken at assessment, as adequate diagnostic work-up in the first instance may have prevented an unnecessary surgical excision biopsy (non-therapeutic) with malignant histology.

6.16 PPV B3 with and without atypia (client)

PPV of B3 with, and without, atypia: measures the percentage of total B3 with atypia results which are malignant on a surgical specimen and the percentage of total B3 without atypia results which are malignant on a surgical specimen. England PPV B3 with atypia: 13.4% (median 11.9%). England PPV B3 without atypia: 5.6% (median 6.2%)

Bar chart showing the proportion of total B3 with atypia results which are malignant on a surgical specimen by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Bar chart showing the proportion of total B3 without atypia results which are malignant on a surgical specimen by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Identifiers shown for 99.7% lower and upper outliers. Plotted against England average of 13.4%.

Funnel plot showing the proportion of total B3 with atypia results which are malignant on a surgical specimen by total number of B3 with atypia results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Identifiers shown for 99.7% upper outliers. Plotted against England average of 5.6%

Funnel plot showing the proportion of total B3 without atypia results which are malignant on a surgical specimen by total number of B3 without atypia results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 3 tab.

Interpretation

As noted above, the recording of the presence or absence of atypia in B3 lesions has not previously been audited in the national pathology audit. The accuracy of recording these data fields will clearly influence the PPV of B3 lesions with and without atypia. Any unit that is an outlier in this measure should consider performing an audit of data accuracy.

6.17 B4 Rate (clients)

NHSBSP standard: minimum <1.5%; preferred <1%. England B4 rate 0.6%

Bar chart showing the B4 rate by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.18 PPV B4 (clients)

This indicator measures the percentage of total B4 results which are malignant on a surgical specimen. England PPV B4: 68.5% (n. 402/587) and median value of 66.7%. Due to very small numbers, providing meaningful performance data is challenging, as hospital laboratory values range from 0% (3 B4 biopsies) to 100% (7 B4 biopsies).

Control chart identifiers shown for 99.7% lower and upper outliers. Plotted against England average of 68.5%.

Funnel plot showing the proportion of B4 results which are malignant on a surgical specimen by total number of B4 results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Interpretation

This metric identifies the percentage of all B4 results which eventually were malignant on a surgical specimen. Most services and laboratories report very few specimens as B4, on either an annual basis or over a longer aggregated period. Caution must therefore be exercised when reviewing this outcome measure. A high PPV B4 could indicate over-caution in reporting of malignancy whilst a low PPV may indicate a low threshold for reporting the suspicious category. It is recommended that the proportion of B3 and PPV of B3 lesions are examined to assess whether there is an excess use of this category. If the PPV of the B3 category is high, this may represent over-caution by the pathologist or sub-optimal sampling by the operator.

6.19 B5 Rate (clients)

Identifiers shown for lower and upper outliers. Plotted against England average of 46.0%.

Funnel plot showing the B5 rate by total number of wide bore needle results by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.20 Proportion of B5 WBN results reported as B5a, B5b or B5c

England biopsies reported as B5a 22.9%, B5b 76.7%, B5c 0.4%.

Bar chart showing the Proportion of B5 wide bore needle results reported as B5a, B5b and B5c by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 1 tab.

6.21 Subsequent surgical histology of clients with a B5a diagnosis on core biopsy

Of biopsies reported as B5a, 17.7% were subsequently invasive at surgery, 78.7% remained as non-invasive and 3.6% of patients had no surgery. The total B5a cases excludes those with benign surgical histology but confirmed as malignancy present on review of the core biopsy, as they are not included in BQA reporting. The small number of false positive (n=14) cases are excluded due to lack of clarity of whether the core biopsy results are B5a or B5b.

Bar chart showing the proportion of B5a biopsies by invasive status at surgery by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 4 tab.

6.22 Absolute sensitivity (clients)

Number of carcinomas diagnosed as such (B5) expressed as a percentage of the total number of carcinomas sampled. NHSBSP standard: >92% (minimum), >95% (preferred). England absolute sensitivity: 97.5% (median 97.8%).

Bar chart showing absolute sensitivity by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

Identifiers shown for lower 99.7% outliers. Plotted against England average of 97.5%

Funnel plot showing absolute sensitivity by total cancers by laboratory

The data displayed in this plot can be found in the attached spreadsheet on the England BQA table 2 tab.

6.23 Complete sensitivity (clients)

Number of carcinomas that were not definitely negative (not B1 or B2) on core expressed as a percentage of the total number of carcinomas. NHSBSP standard: Complete sensitivity >99% (minimum), >99.5% (preferred). England complete sensitivity: 99.9% (median 99.9%). Laboratory hospital range: 99.2% to 100%.

Interpretation

Low outliers for absolute sensitivity should examine rates of complete sensitivity. If this is not also low, or conversely, if it is identified as being a high outlier, the pathologist may possibly be ‘under calling’ B5 cases and categorizing lesions as B3 or B4. This is problematic, as it may result in unnecessary further procedures. However, this may not always be related to histopathology, accuracy of targeting the lesion may be relevant. Methodology may also play a role in this, such as the use of 14 or 16 gauge rather than vacuum-assisted biopsy.

If absolute and complete sensitivity are low, the B1 core biopsy rate from cancers and the false negative rate should be examined, as cancers have been reported non-operatively as B1 or B2. This requires investigation by the radiologists and pathologists, as it may result from either inaccuracy of identification or targeting of the index lesion or from missed diagnosis by the pathologist. It may be valuable to review the MDT decision-making process to identify why no further needle biopsies were undertaken.

6.24 False positive rate

A potential false positive is any case with a B5 core biopsy followed by a normal or benign surgery. Standard: Minimum <0.2%; preferred <0.1%.

The current BQA downloads show inaccurate false positive rates due to the way NBSS analyses data for those cases where cancers have been removed in core biopsies or where there has been complete pathological complete response following neoadjuvant therapy. In addition, some clients are not correctly allocated on NBSS. This is due to their having axillary-only surgery (non-malignant) followed by non-malignant breast surgery (for example where treated by neo-adjuvant chemotherapy with complete pathological response or lesions entirely removed at biopsy). A total of 100 false positive cases are shown on the BQA reports, of which 10 are considered accurate false positives. See companion spreadsheet for details of these.

The PPV of B5 is the only performance measure affected by the number of false positives, as it measures the percentage of total B5 results which are subsequently malignant in a surgical specimen.

7. BQA tables

Tables showing WBN activity and all performance measures can be found in the accompanying spreadsheet. Results are highlighted according to outlier status in control chart analysis.

8. BQA anomalies

Services should clear any exceptions on their BQA downloads. Services should also check and subsequently review B5b to non-invasive surgery clients, B5 to benign/normal surgery clients, and false positive clients.

The accompanying spreadsheet provides a table which shows a summary of results for each region in England. The total number of exceptions accounts for 0.7% of biopsies.

1. Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening”, Non-operative Diagnosis Working Group of the UK National Coordinating Committee for Breast Pathology, The Royal College of Pathologists, June 2016 ↩

2. Quality Assurance Guidelines for Breast Pathology Services - Update to NHSBSP Publication No 2. In press. ↩

3. Guidelines for non-operative diagnostic procedures and reporting in breast cancer screening”, Non-operative Diagnosis Working Group of the UK National Coordinating Committee for Breast Pathology, The Royal College of Pathologists, June 2016 ↩