<prompt> Investigation of choice in DCIS:MammographyCTMRIPET  <response>: Ans. C. MRIDuctal carcinoma-in-situ DCIS and lobular carcinoma-in-situ LCIS are confined to the ducts and acini, respectively. There are four subtypes of DCIS: comedocarcinoma, micropapillary carcinoma, cribriform carcinoma and solid carcinoma. Among these subtypes, comedocarcinoma is the most aggressive. DCIS now accounts for 20-40 of all cancers detected by screening mammography.MRI must be able to demonstrate and characterize mammographically detected lesions including DCIS and, ideally, reveal mammographically occult lesions. This requires MRI to have high-resolution capabilities. 