Inter-observer reproducibility of classical lobular neoplasia (B3 lesions) in preoperative breast biopsies: a study of the Swiss Working Group of breast and gynecopathologists

PURPOSE: Classical type of lobular neoplasia (LN) spans a spectrum of disease, including atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS), classical lobular neoplasia (LN), and the three-tiered classification of lobular intraepithelial neoplasia (LIN-1, -2, -3). This study addressed inter-observer variability of classical lobular neoplasias (LN) (B3 lesions) in preoperative breast biopsies among breast and gynecopathologists METHODS: A retrospective, observational, cross-sectional study was conducted. 40 preoperative digital images of breast core/vacuum biopsies were analyzed by eight experienced breast- and gynecopathologists. Evaluation criteria were ALH, LCIS, LN classic, LIN-1, LIN-2, LIN-3, focal B3 (one focus), extensive B3 (> one focus). Kappa-index and Chi-square tests were used for statistics. Digital scanned slides were provided to each participant. Agreement between the categories was defined as at least six of eight (cut-off 75%) concordant diagnoses. RESULTS: The highest agreement between eight pathologists was reached using the category lobular neoplasia (LN, classical), 26/40 (65%) cases were diagnosed as such. Agreements in other categories was low or poor: 12/40 (30%) (ALH), 9/40 (22%) (LCIS), 8/40 (20%) (LIN-1), 8/40 (20%) (focal B3), 3/40 (7.5%) (LIN-2), and 2/40 (5%) (extensive B3). Chi-square-test (classical LN versus the other nomenclatures) was significant (p = 0.001137). CONCLUSION: Our data suggest that among Swiss breast pathologists, the most reproducible diagnosis for B3 lobular lesions is the category of classical LN. These data further support lack of consistent data in retrospective studies using different terminologies. Validation of reproducible nomenclature is warranted in further studies. This information is useful especially in view of retro- and prospective data analysis with different diagnostic categories.