Carcinoma of the breast is divided into :Carcinoma in situ → neoplastic cells is limited to ducts and lobules by the basement membrane. Invasive carcinoma (infiltrating carcinoma) → cells invade beyond the basement membrane.Caricnoma in situ :It is of two typesA. Ductal carcinoma insitu (DCIS, intraductal carinoma )Most frequently present as manzmographic calcification. Rarely palpable mass may also occur in comedocarcinoma. DCTS is of two types -i. Comedocarcinoma ii. Noncomedo DCTS → Solid, cribriform, papillary or micropapillaryB. Lubular carcinoma in Situ (LCIS)Always an incidental finding in a biopsy performed for another reason. LCIS is not associated with calcification → Therefore, it remains infrequent with or without mammography (in contrast to DCIS) Frequently multicentric and bilateral Signet ring cells are common.