1 - Categorization of Mammographic Density for Breast Cancer: Clinical Significance

Abstract

This chapter describes the mammographic density distribution in breast cancer patients and its relationship to clinicopathological features of tumors and their prognosis and also reviews some recent publications regarding tumor-stromal interaction. Wolfe applied a method of classification of breast density and showed the relationship between mammographic parenchymal patterns and the risk of developing breast cancer. The parenchymal patterns are classified into four categories: N1, P1, P2, and DY. The American College of Radiology (ACR) developed the Breast Imaging-Reporting and Data System (BI-RADS), which is becoming the standard of mammography-reporting terminology and assessment and recommendation categories. The BI-RADS classifies mammographic density into four categories: BI-RADS category 1: breast with the density of fat, BI-RADS category 2: fatty breast with scattered fibroglandular densities, BI-RADS category 3: heterogeneously dense breast, and BI-RADS category 4: dense breast. In most cases, BI-RADS density category is thought to change with patient age. The breast-density categories are significantly correlated with age, but there is heterogeneity of breast density among patients of the same age group. This is probably due to the individual genetic and hormonal status and/or lifestyle effects. The Nottingham Prognostic Index (NPI) score is calculated, which is based on tumor size, node involvement, and Scarff-Bloom-Richardson (SBR) grading, by combining several clinicopathological factors in order to clarify the differences between the BI-RADS breast-density categories. Investigation of patient prognosis after breast surgery excluding deaths from other causes is performed (the mean observation period is 38 months), and there are no significant differences in outcome between the categories.