A critical appraisal of six modern classifications of ductal carcinoma in situ of the breast (DCIS): correlation with grade of associated invasive carcinoma

The in-situ component of 180 cases of screen detected infiltrating duct carcinoma of the breast was classified according to six published classifications for ductal carcinoma in situ based on architecture, necrosis and cytology. All cases were assessed independently by two experienced observers to assess inter-observer variation. The differentiation of ductal carcinoma in situ as assessed by all the classification systems correlated with the grade of the associated invasive carcinoma (chi-squared between 50 and 107: P <0.0001). Disagreements were commonest in the assessment of architecture and least common in the assessment of necrosis. For cytonuclear grade most disagreements (62.2%) involved the distinction between low and intermediate as against 33.9% disagreements for intermediate vs. high. Nuclear grade alone and necrosis alone were correlated with the grade of invasive carcinoma associated with the ductal carcinoma in situ and the Nottingham prognostic index of the patient. The Van Nuys classification of ductal carcinoma in situ is commended because it has a low inter-observer disagreement, is significantly correlated with the grade of the infiltrating carcinoma, uses simple well-defined criteria (with no requirement for percentage estimations), is applicable to small numbers of ducts and, most importantly, appears to correlate with disease-free survival.