REPRODUCIBILITY OF NEW CLASSIFICATION SCHEMES FOR THE PATHOLOGY OF DUCTAL CARCINOMA IN-SITU OF THE BREAST

Aim-To compare the interobserver variation in the pathological classif ication of ductal carcinoma in situ of the breast using two recently p roposed classification schemes. Methods-11 pathologists classified a s et of 25 cases of ductal carcinoma in situ chosen to reflect a range o f lesions, using the traditional architectural classification together with the modified cytonuclear grading scheme of Holland et al and the Van Nuys classification scheme. Participating pathologists received a standard tutorial, written information, and illustrative photomicrogr aphs before their assessment of the cases. Results-Interobserver agree ment was poorest when using the architectural scheme (kappa = 0.44), l argely owing to variations in classifying lesions with a mixed compone nt of patterns (kappa = 0.13). Agreement was better using the modified cytonuclear grading scheme (kappa = 0.57), with most consistency achi eved using the Van Nuys scheme (kappa = 0.66). Most discordant results using the later scheme wee due to inconsistency in assessing the pres ence or absence of luminal necrosis. Conclusions-Both the new classifi cation schemes assessed in this study were an improvement over the tra ditional architectural classification system for ductal carcinoma in s itu, and resulted in more reproducible pathological assignment of case s. The Van Nuys classification scheme is easy to apply, even to small areas of carcinoma, resulting in acceptable interobserver agreement be tween reporting pathologists. Additional work will be required to arri ve at a consensus definition of necrosis for cases in the non-high-gra de group.