How benign breast conditions affect breast cancer risk

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 of the usual type
• Adenosis (non-sclerosing)
• Phyllodes tumor (benign)
• A single (solitary) papilloma
• Granular cell tumor
• Fat necrosis
• Mastitis
• Duct ectasia
• Benign lumps or tumors (lipoma, hamartoma, hemangioma, hematoma, neurofibroma, adenomyoepthelioma)
• Squamous and apocrine metaplasia
• Epithelial-related calcifications

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):

• Moderate or florid ductal hyperplasia of the usual type (without atypia)
• 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 3½ to 5 times higher than normal:

• Atypical ductal hyperplasia
• Atypical lobular hyperplasia

Lobular carcinoma in situ

This condition raises breast cancer risk 7 to 11 times that of normal.