Histopathologic Classification of Breast Cancer in Sweden and Italy: A Comparison between two Pathologists

Interobserver Reproducibility in Diagnosis of Breast Lesions. A Panel in Puglia (Italy)

Background

Given the incidence of breast cancer, histologic agreement is necessary to select the proper treatment.

Methods & study design

Twelve pathologists working in Puglia (Italy) independently evaluated a set of 88 slides of breast lesions. The set included 31 cases which presented difficulties at the moment of first diagnosis (problem cases) and 57 cases without problems (routine cases). Each pathologist was requested to classify lesions according to four categories: A, benign; B, atypical proliferation; C, in situ carcinoma; D, invasive carcinoma. For each case, the definite diagnosis was considered that provided by most of the pathologists (prevalent diagnosis). For the evaluation of degree of agreement, kappa statistics were utilized.

Results

Among routine cases, agreement was observed in 68.4% of cases (38/57) and in 29% of problem cases (9/31). The pair-wise comparison between all participating pathologists showed a good overall agreement, (kappa mean, 0.66; range, 0.57-0.76). The agreement of each pathologist with the prevalent diagnosis was high for invasive (mean kappa, 0.88) and benign lesions (mean kappa, 0.83) followed by in situ carcinoma (mean kappa, 0.64). The lowest value observed was for atypical lesions (mean kappa, 0.25).

Conclusions

The results showed a good overall degree of diagnostic concordance among participating pathologists, all working in the Italian region of Puglia. The findings emerging from the study are comparable to those of other studies performed with selected pathologists specifically specialized in breast pathology. Moreover, the study confirmed the diagnostic difficulties for borderline lesions and the necessity of further investigation for sclerosing lesions with discordant diagnoses.

Estimate of false-positive breast cancer diagnoses from accuracy studies: a systematic review

Background

False-positive histological diagnoses have the same consequences of overdiagnosis in terms of unnecessary treatment. The aim of this systematic review is to assess their frequency at needle core biopsy (CB) and/or surgical excision of the breast.

Methods

PubMed, Embase, Cochrane Library were systematically searched up to 30 October 2015. Eligibility criteria: cross-sectional studies assessing diagnostic accuracy of CB compared with surgical excision; studies assessing reproducibility of pathologists reading the same slides. Outcomes: false-positive rates; Misclassification of Benign as Malignant (MBM) histological diagnosis; K statistic. Independent reviewers extracted data and assessed quality using an adapted QUADAS-2 tool.

Results

Sixteen studies assessed CB false-positive rates. In 10 studies (41 989 screen-detected lesions), the range of false-positive rates was 0%–7.1%. Twenty-seven studies assessed pathologists' reproducibility. Studies with consecutive, random or stratified samples of all the specimens: at CB the MBM range was 0.25%–2.4% (K values 0.83–0.98); at surgical excision, it was 0.67%–1.2% (K values 0.86–0.94). Studies with enriched samples: the MBM range was 1.4%–6.2% (K values 0.57–0.86). Studies of cases selected for second opinion: the MBM range was 0.29%–12.2% (K values 0.48 and 0.50).

Conclusions

High heterogeneity of the included studies precluded formal pooling estimates. When considering studies of higher sample size or methodological quality, false-positive rates and MBM are around 1%. The impact of false-positive histological diagnoses of breast cancer on unnecessary treatment, as well as that of overdiagnosis, is not negligible and is of importance in clinical practice.

Reproducibility of histological diagnosis of breast lesions: results of a panel in Italy

Sixteen pathologists independently examined and classified a series of 81 breast lesions selected from the files of several Italian Pathology Departments in the context of a national task force on breast cancer (FONCAM). A four category classification system was used for analysis; according to the majority diagnosis (MD), simply defined as the most frequently reported in the panel, the series included 37 benign lesions without atypia (45.7%), nine atypical hyperplasias (11.1%), 18 in situ (22.2%) and 17 invasive carcinomas (21.0%). Concordance, estimated for all possible pair-wise comparisons between pathologists, was good (mean kappa value: 0.59). A comparison between the diagnoses of each pathologist and the panel majority diagnosis was also made. Overall, a global kappa value of 0.72 was found (range 0.57-0.85), with category-specific values being excellent for invasive carcinoma (0.89) and benign lesions without atypia (0.77), relatively good for in situ carcinoma (0.69) but poor for atypical hyperplasia (0.38). These results confirm that quality assurance procedures are particularly indicated for large screening programmes for breast cancer, and suggest that for atypical lesions strict diagnostic criteria should be adopted.

Reproducibility of histological diagnoses and diagnostic accuracy of non palpable breast lesions

Twelve pathologists independently examined and classified a set of 25 cases of non palpable breast lesions selected from the archival files of the Pathology Department in Florence. A final consensus diagnosis was reached for all cases at a slide seminar. Individual diagnoses were first combined in 3 broad categories (benign lesion, in situ and invasive carcinoma), then compared to each other and then to the "consensus". Results show that among these 12 pathologists there was complete agreement in 14 cases. Discrepancies for the other 11 cases varied in the number of pathologists and diagnostic categories involved. Overall agreement was excellent (median kappa 0.86) but cases of potentially harmful errors were evident. The authors discuss these findings in the frame of a breast cancer screening program planning.