The 15 Different Types of Breast Cancer (BC)
| Type | Characteristics |
| Ductal carcinoma in situ | Noninvasive BC that starts inside milk ducts, is not life-threatening, and increases risk that invasive BC will develop |
| Invasive ductal carcinoma | Most common type of BC (80% of all cases); more common in women over 55 y old |
| Tubular carcinoma of breast | Small tumors (∼≤1 cm); low-grade and slow-growing |
| Medullary carcinoma of breast | Rare; soft, fleshy mass, affecting women in their late 40s to early 50s; high-grade in appearance, low-grade in behavior; slow-growing; usually does not spread outside breast |
| Mucinous carcinoma of breast (also called colloid carcinoma) | Rare, usually occurring in postmenopausal women; abnormal cells that appear to float in pools of mucin (a key ingredient in mucus) |
| Papillary carcinoma of breast | Rare, usually occurring in older postmenopausal women; well-defined border; small, fingerlike projections; often classified as grade 2 |
| Cribriform carcinoma of breast | Invasion of breast connective tissues by cancer cells in nestlike formations between ducts and lobules, creating distinctive holes with Swiss cheese appearance; usually low-grade |
| Invasive lobular carcinoma (also called infiltrating lobular carcinoma) | Second most common type of BC (10% of all cases of invasive BC); becomes more common as women grow older (two thirds of cases are in women 55 y or older) |
| Inflammatory BC | Rare (1% of all cases of invasive BC) and aggressive; starts with reddening and swelling of breast instead of distinct lump; grows and spreads quickly; is more common in black women and can also affect men |
| Lobular carcinoma in situ | Lobules of abnormal cell growth that increase risk that invasive BC will develop later in life; occurs in premenopausal women (40–50 y old) and is extremely uncommon in men |
| Male BC | Rare (<1% of all cases of BC; in 2019, ∼2,670 men were expected to be diagnosed with BC) |
| Molecular subtypes of BC, based on the genes expressed | Luminal A, luminal B, triple-negative, and HER2-enriched (Table 2) |
| Paget disease of nipple | Rare (<5% of all BC cases in United States); cells collect in or around nipple; 97% of patients also have cancer elsewhere in breast (ductal carcinoma in situ or invasive cancer); unusual changes in nipple and areola are often first indication that BC is present |
| Phyllodes tumors of breast | Rare (<1% of all breast tumors); called phyllodes (“leaflike,” in Greek) because tumor cells grow in leaflike pattern; tends to grow quickly; rarely spreads outside breast |
| Metastatic (stage IV) BC | Spread of cancer to liver, brain, bones, or lungs; will occur in 30% of women diagnosed with early-stage BC (if in bone, metastatic tumor comprises BC cells, not bone cells) |