Breast cancers are classified morphologically according towhether they have penetrated the basement membrane. Those that remain within this boundary are termed in situ carcinomas, and those that have spread beyond it are designated invasive carcinomas. In this classification, the main forms of breast carcinoma are as follows:
A. Noninvasive
- Ductal carcinoma in situ
- Lobular carcinoma in situ
B. Invasive
- Invasive ductal carcinoma (includes all carcinomas thatare not of a special type)—70% to 80%
- Invasive lobular carcinoma— ~10% to 15%
- Carcinoma with medullary features— ~5%
- Mucinous carcinoma (colloid carcinoma) — ~5%
- Tubular carcinoma— ~5%
- Other types (papillary, micropapillary, secretory carcinoma)