Distribution pattern of Ki67 immunoreactivity in ductal intraepithelial neoplasia: Correlation with lesion grade and potential utility

High grade DIN lesions show haphazard Ki67 staining while low grade DIN lesions show basal/peripheral Ki67 staining in the proliferating epithelial cells. This feature could be practical in separating DIN lesions into low grade (basal/peripheral-Ki67) and high grade (haphazard-Ki67) eliminating the grade 2/intermediate category.