Types of Breast Cancer - Breast Cancer Types

Types of Breast Cancer

Breast cancers are named according to the part of the breast they arise from, how far they have spread and how the cancer appears under the microscope. Most breast cancers start in the glands – the lobules or ducts. Cancers beginning in the ducts are called ductal carcinoma and comprise the largest number of breast cancers among women. If the cancer remains in the ducts, and has not spread beyond the cell into surrounding structures, it is called Ductal carcinoma in situ and it accounts for 20-30% of all cancers found on screening mammography.[1] Cancers beginning in the lobules are called lobular carcinomas and refers to cancers that have started in the milk glands or lobules (rather than the ducts). These two types of cancers are both called adenomas because they arise from glandular tissue.

Cancers become invasive when they have spread beyond the boundaries of the cell membrane to surrounding tissues. Invasive breast cancer is broken down as follows according to the type of tissue it arises from. Cancers which arise from the ducts and glands are called Adenocarcinomas. There are two main types and several subtypes.

1. Invasive Ductal Carcinoma
a) cancer cells arising from the ducts which have invaded the surrounding tissue not otherwise specified (75%).

b) subtypes of Ductal carcinoma

Tubular (1%)
Mucinous (1%)
Colloid (1%)
Medullary (1%)
Inflammatory (3-5%)
2. Invasive Lobular Carcinoma
Cancer cells within the lobular tissue of the breast which have invaded surrounding tissue (10 - 15% of all breast cancer).

3. Other
Cancers that arise from epithelial (or skin type cells) are called Squamous carcinomas. They are rare and make up less than 1% of breast cancer. There are also mixed carcinomas (adenosquamous and metaplastic <1%).

Cystosarcoma phyllodes (1%)
A type of sarcoma which is unique to the breast (there is also a non-cancerous type of phyllodes)
Sarcomas (various types <1%) arise from tumours of the connective tissue such as fat, fibrous tissue or blood vessels of the breast)
Lymphomas (various types <1%) arise form white blood cells and rarely start in the breast