Figure 4.

Invasive breast cancers (IBCs) are thought to evolve through a nonobligatory series of increasingly abnormal “stages,” referred to as hyperplasia, atypical hyperplasia, and carcinoma in situ over long periods of time, probably decades in most cases. Ductal carcinoma in situ (DCIS) is the main type of carcinoma in situ in the breast (80%–90%) and a late stage of breast cancer evolution. Many types of evidence support the hypothesis that DCIS are the immediate precursor of IBCs, including points of histological continuity (right photomicrograph).