The NHS breast screening programme (pathology) EQA: experience in recent years relating to issues involved in individual performance appraisal

Screen-detected ductal carcinoma in situ, 2008-2020: An observational study

OBJECTIVES

The purpose of this study was to evaluate the grade distribution of screen-detected ductal carcinoma in situ (DCIS) diagnosed in Ireland, in the context of the clinical trials currently underway to determine if active surveillance is a feasible management option for low-risk DCIS.

SETTING

BreastCheck is the national breast screening programme in Ireland, offering screening to women aged 50 to 69 every two years.

METHODS

This study was a secondary analysis of data collected by BreastCheck on all screen-detected DCIS diagnosed in the 12 years of nationwide screening. Incidence and detection rates were calculated. Descriptive analysis of the cases was performed and, for comparative analysis, grade of DCIS was analysed as a binary variable (high vs. low/intermediate) in keeping with the inclusion criteria for active surveillance trials. Analysis was performed in IBM Statistical Package for Social Sciences, version 26.

RESULTS

Between 2008 and 2020, 2240 women were diagnosed with DCIS through BreastCheck; 876 (39.1%) were low/intermediate-grade. The overall incidence rate has remained relatively stable during this period. Women with low/intermediate-grade DCIS were younger than women with high-grade DCIS (56 (interquartile range: 56-61) years v 57 (interquartile range: 53-61) years; p < 0.001). They were also more likely to have been diagnosed at an initial screening episode compared with those who had high-grade lesions (42.5% v 29.0%; p < 0.001).

CONCLUSION

If current clinical trials recommend active surveillance as a feasible option for DCIS, up to 40% of women with screen-detected DCIS may be eligible. These women are younger and often diagnosed on initial screening episode, so may require longer active follow-up.

Nuclear morphology in breast lesions: refining its assessment to improve diagnostic concordance

BACKGROUND

Although evaluation of nuclear morphology plays a crucial role in the diagnosis and categorisation of breast lesions, the criteria used to assess nuclear atypia rely on the subjective evaluation of several features that may result in inter- and intra-observer variation. This study aims to refine the definitions of cytonuclear features in various breast lesions.

METHODS

ImageJ was used to assess the nuclear morphological features including nuclear diameter, axis length, perimeter, area, circularity, and roundness in 160 breast lesions comprising ductal carcinoma in situ (DCIS), invasive breast carcinoma of no special type (IBC-NST), tubular carcinoma, usual ductal hyperplasia (UDH), columnar cell change (CCC) and flat epithelial atypia (FEA). Reference cells included normal epithelial cells, red blood cells (RBCs) and lymphocytes.

RESULTS

Reference cells showed size differences not only between normal epithelial cells and RBCs but also between RBCs in varied-sized blood vessels. Nottingham grade nuclear pleomorphism scores 1 and 3 cut-offs in IBC, compared to normal epithelial cells, were <1.2x and >1.4x that of mean maximum Feret's diameter and <1.6x and >2.4x that of mean nuclear area, respectively. Nuclear morphometrics were significantly different in low-grade IBC-NST vs. tubular carcinoma, low-grade DCIS vs. UDH, and in CCC vs. FEA. No differences in the nuclear features between grade matched DCIS and IBC were identified.

CONCLUSION

This study provides a guide for the assessment of nuclear atypia in breast lesions, refines the comparison with reference cells and highlights the potential diagnostic value of image analysis tools in the era of digital pathology.

Diagnostic concordance of phyllodes tumour of the breast

AIMS

Phyllodes tumours (PT) are rare and distinct breast tumours, which span a morphological continuum. Classification into benign, borderline and malignant categories reflects their biology and clinical behaviour and is essential to guide management. This study aims to assess the diagnostic agreement of PT using the UK National Health Service Breast Screening Programme (NHSBSP) breast pathology external quality assurance (EQA) scheme data.

METHODS AND RESULTS

Twenty-six PTs were identified in the EQA scheme, which were diagnosed by an average of 607 participants/circulation. Data on diagnostic categories were collected and representative slides were reviewed. The level of concordance between reporting pathologists was assessed. There were 14 benign, six borderline and six malignant PT. The overall rate of diagnosis agreement was 86% when analysed as benign lesions, borderline PT and malignant lesions, which decreased to 79% when diagnosed as PT (irrespective of grade) and to 63% when the diagnosis was further refined to PT categories (benign, borderline and malignant PTs). The highest agreement rate was observed in malignant PT (86%) and the lowest in borderline PT (42%). Malignant heterologous elements, stromal overgrowth and leaf-like architecture are features associated with higher concordance rates. Lower-priority features were stromal expansion, clefting and multinodularity.

CONCLUSION

The concordance of PT diagnosis, as an entity, is high, but its classification into benign, borderline and malignant has variable agreement levels, with borderline tumours having the lowest concordance rate. More research to refine the diagnostic criteria for categorisation of PT is warranted to improve concordance between pathologists.

Technical Factors Affecting Ultrasound Breast Tumor Size as Correlated with Pathological Type

Background and Objectives: Accurate breast tumor sizing is very important in treatment planning; as a result, ultrasound (US) plays an important role in diagnosing breast masses, due to its non-magnified image and its availability. The continuous change in the disease pathogenesis of breast cancer and tremendous advances in US imaging technology require the continuous evaluation of this imaging modality. In this study, our aim was to determine the accuracy of US in measuring the size of breast mass, and if there is an influence of the different pathological types on this accuracy. Materials and Methods: This study contained 66 specimens of breast masses that underwent surgical excision and pathological examination of the resected masses; the mean difference between the size taken by US and the size taken by pathology was calculated to the patients as a whole and for each tumor type in this study. Results: The result was that US underestimates the size of the tumor by 0.5 cm for all pathological types, and the US size is in agreement with the pathology size. Conclusions: US is an accurate method in measuring breast lesions with a degree of underestimation that may be related to many factors such as the tumor type, size, and margins. Complementary MRI is recommended in case of ILC and architectural distortion.

Diagnostic concordance of reporting lymphovascular invasion in breast cancer

AIMS

This study aims to assess the diagnostic agreement of lymphovascular invasion (LVI) in invasive breast cancer (BC).

METHODS

Data on LVI were collected from the UK National Health Service Breast Screening Programme pathology external quality assurance scheme database. 101 BCs assessed over a 10-year period (2004-2014) were included. Cases were scored by an average of 600 pathologists. Three H&E stained slides from each case were reviewed by three pathologists and additional variables were evaluated.

RESULTS

In the whole series, the overall κ value was 0.4 (range 0.26-0.53). On review, LVI was detected in all three slides in 20 cases (20%), in two slides in 12 cases and in one of the three slides in 9 cases and was not seen in 60 cases. For concordance analysis, the first and last groups were used to represent cases with definite (LVI+) and absent LVI (LVI-), respectively. In the LVI+group (n=20), the level of agreement ranged from 0.54 to 0.99 (median 0.86). In the LVI- group (n=60), the level of agreement ranged from 0.52 to 1.00 (median 0.93), with 44% of cases showing interobserver concordance of >95%. There was a correlation between increasing number of involved lymphovascular spaces in the section and higher LVI reporting concordance. Some degree of retraction/fixation artefacts was observed in 35% of cases; this was associated with a lower concordance rate.

CONCLUSIONS

The concordance of reporting LVI is variable. Cases without LVI and those with multiple involved vessels are likely to have the highest concordance and the highest detection rates.

Can reference images improve interobserver agreement in reporting liver fibrosis?

Staging of fibrosis in medical liver biopsies has inherent interobserver variability. There are a number of disease-specific scoring systems available. While recognising the importance of these scoring systems, there is scope to consider how concordance amongst histopathologists could be improved using a generic fibrosis staging system.

Using virtual slides, we approached both specialist liver histopathologists and general histopathologists from the UK to assess the degree of fibrosis against a proposed four-tiered reporting system. Example reference images were then produced and distributed to the same responders who were asked to rate a second set of slides to assess if the use of reference images improved concordance between pathologists.

The use of reference images eliminated spread across three categories (from 15% to 0%). Overall, agreement was already good; our study showed an improved agreement amongst all participants for percentage agreement (67.79% to 70.08%) and interobserver agreement improved (Fleiss’ Kappa 0.55 to 0.59).

Papillary carcinoma of the breast: diagnostic agreement and management implications

AIMS

Papillary carcinoma (PC), which is a rare type of breast cancer, comprises a heterogeneous group of tumours. The diagnostic categorization of PC as in-situ and invasive disease remains a matter of debate with respect to interpretation of its overlapping histological features, and with respect to the uncertainty in clinical behaviour that this dilemma raises. The aim of this study was to assess the diagnostic agreement regarding PC among reporting breast pathologists.

METHODS AND RESULTS

Six cases of PC included in the UK National Health Service Breast Screening Programme breast pathology interpretive external quality assurance scheme in the last 10 years were reviewed. In this scheme, one representative haematoxylin and eosin-stained slide from each case is circulated to an average of 600 participants. Data on diagnostic categories were collected and slides were reviewed according to the World Health Organization (WHO) diagnostic criteria. The number of final diagnoses of malignancy (in situ or invasive) was highest for invasive PC (99% of the participants diagnosed it as malignant), followed by solid PC (94% and 95%, respectively), encapsulated PC (92% and 92%, respectively), and papillary ductal carcinoma in situ (DCIS) (88%). Most cases of papillary DCIS were correctly classified as in-situ disease (77%), but 28% of the participants classified invasive PC cases as in-situ disease. Of the participants, 24% reported encapsulated PC as invasive disease. Of the two solid PC cases, one showed some features consistent with the WHO description of invasive solid PC, whereas the other showed features of classic (non-invasive) solid PC. Both cases were reported as invasive by 75% and 77% of participants, respectively. Breast specialists more frequently classified PC as an in-situ carcinoma than did non-specialist participants, and the difference was significant (P = 0.013).

CONCLUSIONS

Recognition of PC as a malignant entity (in situ or invasive) is high, but concordance of its classification into in-situ and invasive disease is low. Histological features that can define invasion in PC should be better defined. These rare lesions require additional diagnostic work-up, and difficult cases should trigger consensus opinion or expert referral.

Review of the national external quality assessment (EQA) scheme for breast pathology in the UK

Background

The National Health Service Breast Screening Programme (NHSBSP; pathology) external quality assurance (EQA) scheme aims to provide a mechanism for examination and monitoring of concordance of pathology reporting within the UK. This study aims to review the breast EQA scheme performance data collected over a 24-year period following its introduction.

Methods

Data on circulations, number of cases and diagnosis were collected. Detailed analyses with and without combinations of certain diagnostic entities, and over different time periods were performed.

Results

Overall, of 576 cases (172 benign, 11 atypical hyperplasia, 98 ductal carcinoma in situ/microinvasive and 295 invasive disease), consistency of assessment of diagnostic parameters was very high (overall k=0.80; k for benign diagnosis=0.79; k for invasive disease=0.91). For distinguishing benign versus malignant lesions, no further improvement is considered possible in view of the limitations of the scheme methodology. Although diagnostic consistency of atypical hyperplasia remains at a low level, combining it with the benign category results in a high level of agreement (k=0.93). The level of consistency of reporting prognostic information is variable and some items such as lymphovascular invasion and tumour size measurement may need further intervention to improve their reporting consistency. Although the level of consistency of reporting of histological grade remained at a moderate level overall (k=0.48), it was variable among cases and appears to have levelled off; no further significant improvement is expected and no significant impact of the previous publication of guidelines is observed.

Conclusions

These results provide further evidence to indicate the value of the breast EQA scheme in monitoring performance and the identification of specific areas where improvement or new approaches are required. For most parameters, the concordance of reporting reached a plateaux a few years after the introduction of the EQA scheme. It is important to maintain this high level and also to tackle specific low-performance areas innovatively.

Measuring interobserver variation in a pathology EQA scheme using weighted κ for multiple readers

Background

A Urological Pathology External Quality Assurance (EQA) Scheme in the UK has reported observer variation in the diagnosis and grading of adenocarcinoma in prostatic biopsies using basic κ statistics, which rate all disagreements equally.

Aim

The aim of this study is to use customised weighting schemes to report κ statistics that reflect the closeness of interobserver agreement in the prostate EQA scheme.

Methods

A total of 83, 114 and 116 pathologists took part, respectively, in three web-based circulations and were classified as either expert or other readers. For analyses of diagnosis, there were 10, 8 and 8 cases in the three circulations, respectively. For analyses of Gleason Sum Score, only invasive cases were included, leaving 5, 5 and 6 cases, respectively. Analyses were conducted using customised weighting schemes with ‘pairwise-weighted’ κ for multiple readers.

Results

Analysis of diagnosis for all circulations and all readers gave a composite κ value of 0.86 and pairwise-weighted κ (κp–w) value of 0.91, both regarded as ‘almost perfect’ agreement. This was due to the high proportion of responses that showed partial agreement. Analysis of Gleason Sum Score gave κ=0.38 and κp–w=0.58 over all circulations and all readers, indicating that discrepancies occur at the boundary between adjacent grades and may not be as clinically significant as suggested by composite κ.

Conclusion

Weighted κ show higher levels of agreement than previously reported as they have the advantage of applying weighting, which reflects the relative importance of different types of discordance in diagnosis or grading. Agreement on grading remained low.

External quality assessment for KRAS testing is needed: setup of a European program and report of the first joined regional quality assessment rounds

The use of epidermal growth factor receptor-targeting antibodies in metastatic colorectal cancer has been restricted to patients with wild-type KRAS tumors by the European Medicines Agency since 2008, based on data showing a lack of efficacy and potential harm in patients with mutant KRAS tumors. In an effort to ensure optimal, uniform, and reliable community-based KRAS testing throughout Europe, a KRAS external quality assessment (EQA) scheme was set up. The first large assessment round included 59 laboratories from eight different European countries. For each country, one regional scheme organizer prepared and distributed the samples for the participants of their own country. The samples included unstained sections of 10 invasive colorectal carcinomas with known KRAS mutation status. The samples were centrally validated by one of two reference laboratories. The laboratories were allowed to use their own preferred method for histological evaluation, DNA isolation, and mutation analysis. In this study, we analyze the setup of the KRAS scheme. We analyzed the advantages and disadvantages of the regional scheme organization by analyzing the outcome of genotyping results, analysis of tumor percentage, and written reports. We conclude that only 70% of laboratories correctly identified the KRAS mutational status in all samples. Both the false-positive and false-negative results observed negatively affect patient care. Reports of the KRAS test results often lacked essential information. We aim to further expand this program to more laboratories to provide a robust estimate of the quality of KRAS testing in Europe, and provide the basis for remedial measures and harmonization.

Experts and performance in histopathology--a study in breast pathology

This study was undertaken to determine if it was possible to identify expertise within Histopathologists (trainees, district general pathologists and pathologists with a special interest in breast disease) using an objective measure of performance. The method of assessment of performance is based on the CWS (Cochran-Weiss-Shanteau) ratio formed by the individual's ability to discriminate between a spectrum of disease categories and their level of inconsistency when assessed at intervals. The slides circulated represented the spectrum of breast disease seen in routine practice. The results demonstrated the average CWS ratio to be lowest in trainees and highest in pathologists with a special interest in breast pathology although there was no statistical difference in the CWS scores obtained between the district general pathologists and pathologists with a special interest. Differences in inconsistency rather than discriminatory ability mainly accounted for the difference in the CWS ratio observed between the groups studied. The study shows that the CWS ratio is potentially a very useful tool in the assessment of pathologists with regard to assessing their progress through training.

Pattern and spectrum of morphology referrals in breast pathology consultation

AIMS

We aimed to identify common reasons for second opinion breast pathology referrals at the Pathology Department, Singapore General Hospital, focusing on queries and diagnostic issues raised by referring clinicians and pathologists.

METHODS

Request forms for breast pathology consultations were retrieved from a specialist's correspondence files consisting of pathologists' referrals, and from centralised laboratory records, comprising clinician-initiated referrals. Clinical and histomorphological queries raised by the referrals were collated.

RESULTS

Of 299 cases evaluated, clinician-initiated referrals (n = 137, 46%) included requests for review of overall histopathology to confirm carcinoma subtype (n = 47), grade (n = 2), size (n = 4), lymphovascular invasion (n = 1) and confirm hormonal receptor and c-erbB-2 assays (n = 33). Also required were: comparison of recurrent with previous lesions (n = 8); settling discrepant diagnoses between two or more prior pathology reports (n = 4); verification of microinvasion (n = 6), in situ carcinomas (n = 6) or atypical ductal hyperplasias (n = 4); delineation of benign (n = 8) and spindle cell lesions (n = 3); to establish a breast origin of metastatic lesions (n = 5); and distinction of carcinoma from lymphoma (n = 2). Pathologist-initiated referrals (n = 162, 54%) sought arbitration between borderline proliferative lesions (n = 46) and papillary lesions (n = 34); verification of microinvasion (n = 23), stromal lesions (n = 16), and carcinoma subtype (n = 13), especially if the patient was young (n = 5); clarification of metaplastic changes (n = 4) and lobular neoplasia (n = 8); and comparison of fibroepithelial lesions (n = 11).

CONCLUSIONS

Clinicians sought a second opinion mainly to verify histological diagnoses and report important pathological details for staging and confirmation of hormonal receptor and c-erbB-2 status prior to therapy. Borderline breast lesions are worrisome for both clinicians and pathologists in view of implications for management.