There are two forms of ductal carcinoma -- in situ, which is noninvasive cancerous cell growth within the milk ducts, and invasive ductal carcinoma, which is cancerous cell growth that has invaded the tissues beyond the milk ducts. Ductal carcinoma in situ is the earliest stage at which breast cancer can be diagnosed, and while most cases are curable, medical treatment is necessary to prevent invasive cancer. Invasive ductal carcinoma comprises most invasive breast cancers, and, depending on where it has spread, requires more aggressive treatment. Both cancers are detectable by mammography. Follow the links below to find WebMD's comprehensive coverage about the forms of ductal carcinoma, how ductal carcinoma is detected, diagnosed, and treated, and much more.