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.

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.

Locally organised medical audit in histopathology

The principles behind medical audit are straightforward, and histopathology departments are not exempt from the increasing requirement for audit in hospitals throughout the United Kingdom. Participation in a local audit scheme can offer more direct benefits than those which may be achieved by participation in a diagnosis based external quality assurance system, but the two are not incompatible. Histopathology Departments should establish their own system, developing an audit strategy for their particular laboratory and obtaining funding in advance. The experience gained from Southampton would suggest that such local systems are best kept fairly straightforward, so that they can be managed readily and do not become too onerous. Individual departments should institute a forum for presenting the results of their audit, and should consider how they might go about correcting any inadequacies detected by their system. It is also important for a department to decide on the extent up which their findings are to be disseminated more widely, in particular to the administration and managerial staff of their institute.