There are two main groups of diffuse breast cancers presenting on the mammogram as large regions of architectural distortion; these account for about 25% of all breast cancers and tend to have a poor outcome: 1) Neoductgenesis, i.e. “duct forming invasive carcinoma”, the topic of this volume, often erroneously diagnosed as “DCIS”, and 2) Diffusely infiltrating breast cancer, the topic of Vol. XI. This volume demonstrates the DAB subgroup where the unnaturally high concentration of abnormal, tumor-filled ducts results in an asymmetric density with architectural distortion on the mammogram and often causes a palpable “thickening”. Detecting architectural distortion on the mammogram and diagnosing the underlying disease correctly is a challenge for the radiologist. Breast cancers originating from the major ducts (DAB) are characterized by the formation of new, duct-like structures through the process of Neoductgenesis.