Breast cancer is not just one disease. The type of breast cancer depends on where it begins in the breast and the biology of the cancer cells. Understanding the type helps doctors design the best treatment plan.

Common types

Ductal Carcinoma In Situ (DCIS)

• Stage 0 (non-invasive) cancer.
• Abnormal cells are found in a milk duct but have not spread.
• Highly treatable and often found on screening mammograms.

Invasive Ductal Carcinoma (IDC)

• The most common type (about 70–80% of cases).
• Starts in the milk ducts, then invades nearby breast tissue.
• Can spread to lymph nodes and beyond.

Invasive Lobular Carcinoma (ILC)

• Starts in the lobules (milk-producing glands).
• Second most common invasive type.
• May be harder to detect on mammogram, often found later.

Less common types

Inflammatory Breast Cancer (IBC)

• Rare and aggressive.
• Causes breast redness, swelling, and warmth instead of a lump.

Paget’s Disease of the Breast

• Cancer cells affect the skin of the nipple and areola.

Phyllodes Tumor

• Rare; can be benign or malignant. Starts in the connective tissue.

Angiosarcoma

• Extremely rare; develops in blood or lymph vessels of the breast.

Biological subtypes (based on cell markers)

Doctors test breast cancer cells for proteins and hormone receptors. These results guide treatment:

Hormone Receptor-Positive (ER+/PR+)

• Cancer cells grow with estrogen or progesterone.
• Often treated with hormone (endocrine) therapy.

HER2-Positive

• Cancer cells have too much HER2 protein.
• More aggressive but respond to targeted drugs.

Triple-Negative Breast Cancer (TNBC)

• Lacks estrogen, progesterone, and HER2.
• Tends to grow faster and has fewer targeted treatments.

Why knowing the type matters

• Helps predict how the cancer may behave.
• Guides treatment (surgery, radiation, hormone therapy, chemotherapy, or targeted therapy).
• Provides insight into prognosis.