Breast parenchymal patterns: prevalent and incident carcinomas.

Breast parenchymal patterns can be divided into four groups: N1, P1, P2 and DY. Although there is evidence that the P2-DY group favors the development of cancer, the risk classification changes when one considers prevalent vs. incident breast cancers. In a purely incident series, a gradual diminution will be seen in the number of N1-P1 cancer cases and a corresponding rise in cancer patients from the P2-DY group.