As noted earlier, some types of benign breast conditions are linked to higher breast cancer risk, while others are not. Doctors often divide benign breast conditions into 3 general groups, based on whether the cells are multiplying (proliferative) and whether there are abnormal cells or patterns of cells (atypia):
- Non-proliferative lesions do not seem to affect cancer risk
- Proliferative lesions without atypia slightly increase cancer risk
- Proliferative lesions with atypia raise the risk of cancer
Non-proliferative lesions
These conditions are not linked with the overgrowth of breast tissue. They do not seem to affect breast cancer risk, or if they do, the effect is very small. They include:
- Fibrosis
- Cysts
- Mild hyperplasia
- Adenosis (non-sclerosing)
- Simple fibroadenoma
- Phyllodes tumor (benign)
- A single (solitary) papilloma
- Granular cell tumor
- Fat necrosis
- Mastitis
- Duct ectasia
- Benign lumps or tumors (lipoma, hamartoma, hemangioma, hematoma, neurofibroma)
Proliferative lesions without atypia
These conditions are linked with the growth of cells in the ducts or lobules of the breast tissue. They seem to raise a woman's risk of breast cancer slightly (1½ to 2 times the usual risk):
- Usual ductal hyperplasia (without atypia)
- Complex fibroadenoma
- Sclerosing adenosis
- Multiple papillomas or papillomatosis
- Radial scar
Proliferative lesions with atypia
These conditions are linked with the excess growth of cells in the ducts or lobules of the breast tissue, and the cells no longer look normal. They can raise breast cancer risk about 4 to 5 times higher than normal:
- Atypical ductal hyperplasia
- Atypical lobular hyperplasia
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