The efficacy and limitations of repeated slide conferences for improving interobserver agreement when judging nuclear atypia of breast cancer

Background: The pathology section of the Japan National Surgical Adjuvant S tudy of Breast Cancer protocol study was set up to establish histological c riteria for assessing high-risk node-negative breast cancers and standardiz e the subjective criteria used by collaborating pathologists for nuclear gr ading of cancers. Methods: in order to standardize the nuclear atypia criteria, five slide co nferences were held. A total of 57 observers assigned nuclear atypia scores to 119 breast carcinomas that were presented using a slide projector or a TV monitor and discussed their histological findings. The percentage intero bserver agreements per tumor and per conference and re value per conference were estimated and compared among the conferences. The percentage intraobs erver reproducibility per tumor between the last two conferences was compar ed with the percentage interobserver agreement for 20 tumors. The kappa val ue was also calculated for each of 27 observers to evaluate scoring reprodu cibility. Results: The percentage interobserver agreement per conference was constant (75-78%) throughout the five meetings and the rate of tumors with >80% agr eement per tumor became higher in later conferences. The K value was 0.42, 0.25, 0.42, 0.51 and 0.50 for the first, second, third, fourth and fifth co nferences, respectively. The tumors with a lower percentage interobserver a greement also had a lower percentage intraobserver reproducibility and such scoring variations were attributed to the intermediate nature of the degre e of tumor atypia. In 26 of 27 observers, intraobserver agreement for 20 tu mors was estimated from the re value to range from moderate to almost perfe ct. Conclusion: We concluded that the repeated slide conferences conducted by t he pathology section were an effective means of standardizing the subjectiv e histopathological criteria used to assess tumors. However, the achievemen t of a good scoring agreement would be difficult for tumors with an interme diate degree of atypia.