The Types of Breast Cancer Explained

Breast cancer begins when cells in the breast grow abnormally. Sometimes those cells form a lump you can feel. Other times, cancer develops without obvious symptoms right away, especially in its early stages. Annual mammograms can help detect breast cancers before symptoms appear.  

If you are diagnosed with breast cancer, understanding the different types can help you make sense of your diagnosis and treatment options. It can also explain why your care team might suggest certain tests or therapies.

Northwestern Medicine Breast Surgeon Denise A. Monahan, MD, explains the most common types of breast cancer, along with some less common and rare forms.

The Most Common Types of Breast Cancer

To understand breast cancer types, it helps to know a little about breast anatomy. The breast has three main parts:

• Lobules, which make milk
• Ducts, which carry milk to the nipple
• Connective tissue, which consists of fat and fibrous material that supports the breast

Most breast cancers begin in the ducts or the lobules.

Ductal Carcinoma in Situ (DCIS)

DCIS means abnormal cells are found only inside the milk ducts. Doctors consider this noninvasive breast cancer because it hasn’t spread beyond the ducts.

Although DCIS is an early-stage condition, it can occur alongside or progress to invasive cancer, so doctors typically recommend treatment.

Lobular Carcinoma in Situ (LCIS)

LCIS starts in the lobules, the milk-producing glands. Despite its name, LCIS is not considered cancer. Instead, it is a marker that indicates a higher risk of developing breast cancer later.

Surgery may be recommended in rare situations, but LCIS is mainly managed with close monitoring, imaging and strategies to lower breast cancer risk, such as preventive medication.

Invasive Breast Cancer

Invasive (or infiltrating) breast cancer means cancer cells have spread beyond the ducts or lobules into nearby breast tissue. The two most common invasive breast cancers are:

• Invasive ductal carcinoma
• Invasive lobular carcinoma

Invasive Ductal Carcinoma (IDC)

IDC is the most common type of breast cancer. It begins in the milk ducts and can spread into surrounding breast tissue. About 80% of breast cancers in the United States are IDC.

Invasive Lobular Carcinoma (ILC)

ILC starts in the lobules and can spread into nearby breast tissue. It can be harder to detect on mammograms, so doctors sometimes recommend a breast MRI for further evaluation. ILC accounts for about 10% to 15% of breast cancers in the United States.  

“Both invasive and noninvasive breast cancer are usually treated with surgery first,” says Dr. Monahan. “Sometimes, patients with certain types of invasive cancer — or cancer that has already spread to lymph nodes — may receive chemotherapy before surgery.”

Noninvasive breast cancer is not treated with chemotherapy, she adds. Your care team will explain your treatment plan and sequence of care.

Less Common and Rare Types of Breast Cancer

Some breast cancers are less common, but it’s still important to recognize them.

Paget Disease of the Breast

Paget disease of the breast affects the skin of the nipple and areola. Symptoms may include redness, flaking, itching or irritation that doesn’t go away. It is a rare, noninvasive form of breast cancer.

Inflammatory Breast Cancer (IBC)

Inflammatory breast cancer is rare but aggressive. Instead of a lump, symptoms often include swelling, redness, warmth, or skin that looks thickened or dimpled, like an orange peel. These symptoms can appear quickly, so IBC requires urgent medical attention.

Phyllodes Tumors

Phyllodes tumors grow in the connective tissue of the breast. Most are benign, but some can be cancerous and grow quickly. Surgery is usually the main treatment.

Rare Invasive Breast Cancers

Medullary, mucinous and tubular breast cancers are rare forms of invasive breast cancer. Their names come from how the cells look and behave under a microscope.

Metaplastic carcinoma is another rare type of breast cancer. It can grow quickly and often contains a mix of different cell types, which pathologists identify during examination.

Breast Cancer Based on Tumor Biology

Doctors also classify breast cancer based on tumor biology — how cancer cells behave at a molecular level. These molecular subtypes of cancer help guide treatment decisions.

HER2-Positive Breast Cancer

Some breast cancers produce high levels of a protein called HER2, which stands for human epidermal growth factor receptor 2. These cancers tend to grow faster, but targeted therapies have significantly improved outcomes.

Triple-Negative Breast Cancer

Triple-negative breast cancer does not respond to hormone therapy or HER2-targeted treatments. It tends to be more aggressive and is more common in younger patients and those with certain inherited gene mutations.

Metastatic Breast Cancer

Metastatic breast cancer means the cancer has spread to other parts of the body, such as the bones, lungs, liver or brain.

It is not a separate type of cancer, but an advanced stage. Treatment focuses on managing the disease, easing symptoms and maintaining quality of life.

Breast Cancer in Men

Although it’s rare, men can get breast cancer, too. Symptoms may include a lump, nipple changes or thickening of the skin. Any new or unusual breast changes should be evaluated by a doctor, regardless of gender. Treatment depends on the type and stage.

“Our team works together to support our patients during diagnosis, treatment and moving forward,” says Dr. Monahan. “We take a collaborative approach to developing personalized treatment plans for patients with breast cancer.”

Personalized Treatment Options and the Importance of Early Detection

Breast cancer is still the second leading cause of cancer-related deaths in women, after lung cancer. At the same time, treatment options continue to improve.

Advances in precision medicine allow clinicians to tailor treatments to each patient, even those with metastatic breast cancer. Clinical trials and ongoing research are expanding options and improving outcomes.

Early detection remains one of the most important tools in breast cancer care. Finding cancer early often makes it easier to treat and provides more options. Staying informed, watching for changes and following recommended screening guidelines can help protect your breast health.

“Breast cancer treatment has made great progress and continues to improve,” says Dr. Monahan. “But early detection leads to the best outcomes. If you notice any changes or have concerns, talk to your doctor.”

Learn more about comprehensive breast care, including advanced treatments, research and support services.