Invasive Breast Cancer

April 10, 2025

This page was reviewed under our medical and editorial policy by Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

Invasive breast cancer is the most common type of breast cancer. It occurs when cancer cells spread from the milk ducts or lobules into the surrounding breast tissue.

This type of breast cancer is also known as infiltrating breast cancer. While most breast cancers are invasive, the disease has different forms, each with unique characteristics.

Understanding invasive breast cancer and its symptoms, types and treatment options may help patients and their families feel more informed and prepared when facing a diagnosis.

What Is Invasive Breast Cancer?

Invasive breast cancer occurs when cancer cells spread from where they first developed in the breast into nearby tissue. It may start in different places within the breast, and each type has different cell features.

In some cases, invasive breast cancer does not just stay in the breast tissue. It may spread (metastasize) to other body parts through the blood or lymph systems, which is why early detection and treatment are important.

Most breast cancers occur randomly, with only a small percentage linked to inherited genetic mutations, like BRCA1 and BRCA2. Testing the tumor for hormone receptors, such as estrogen, progesterone and HER2, is another important part of understanding how the cancer may grow and which treatments may be most appropriate.

Because there are different types of invasive breast cancer, the outlook for each patient varies. The prognosis often depends on how early the cancer is detected, the specific type and whether it has spread.

Types of Invasive Breast Cancer

There are several types of invasive breast cancer, each with its own characteristics. Here is a brief overview of the most common types.

Invasive Ductal Carcinoma (IDC)

Invasive ductal carcinoma is the most common type of invasive breast cancer, accounting for about 80% of cases. It begins in cells lining the milk ducts and then spreads into nearby breast tissue. From there, IDC may move into the lymph system and bloodstream, potentially affecting other body parts.

Invasive Lobular Carcinoma (ILC)

Invasive lobular carcinoma accounts for about 10% of invasive breast cancers. It begins in the glands that produce milk (lobules) and may spread similarly to IDC. Invasive lobular carcinoma may be harder to detect through imaging and physical exams, and it is more likely to affect both breasts. In about 20% of cases, cancer is found in both breasts at the time of diagnosis.

Inflammatory Breast Cancer (IBC)

Inflammatory breast cancer is a rare and aggressive form of breast cancer, making up about 1% to 5% of cases. It gets its name because the breast often looks red, swollen and inflamed from cancer cells blocking lymph vessels in the skin. IBC is a type of invasive ductal carcinoma, but it behaves differently and has distinct symptoms and treatment options.

Triple-Negative Breast Cancer (TNBC)

Triple-negative breast cancer is another aggressive form of invasive breast cancer that does not respond to hormone or HER2 medications because the cancer cells do not have estrogen or progesterone receptors and do not overproduce the protein HER2. “Triple negative” refers to the fact that samples of the cancer test negative for these three components. TNBC tends to grow and spread quickly. It also has fewer treatment options compared to other types of invasive breast cancer.

Triple-Positive Breast Cancer (TPBC)

Triple-positive breast cancer is a type of invasive breast cancer where the cancer cells have estrogen receptors, progesterone receptors and more than the usual number of HER2 receptors. TPBCs are treated with hormone therapy and drugs that target the HER2 protein.

Some of the types above may be further classified as luminal A, luminal B and HER2-positive, based on their hormone and protein receptors.

There are many other subtypes of invasive breast cancer, but they are less common than those above.

 Some of the subtypes are more aggressive, and some are less aggressive, than the most common type of invasive breast cancer, IDC.

These subtypes include:

• Adenoid cystic carcinoma
• Low-grade adenosquamous carcinoma
• Medullary carcinoma
• Metaplastic carcinoma
• Micropapillary carcinoma
• Mixed carcinoma (has features of both IDC and ILC)
• Mucinous (or colloid) carcinoma
• Papillary carcinoma
• Tubular carcinoma

Invasive Breast Cancer Symptoms

The symptoms of invasive breast cancer may vary depending on the type and how advanced it is. In many cases, patients do not have any noticeable symptoms, and the cancer is found during routine exams or mammograms. However, as the cancer grows, some people may feel a lump in the breast.

In more advanced stages, other symptoms might appear, such as thickening or dimpling of the skin. This is sometimes called peau d'orange because it looks like the skin of an orange. Other signs might include changes in the nipple, such as discharge, swelling or ulceration. Inflammatory breast cancer may cause redness, swelling and warmth in the breast, which may look similar to an infection.

If the cancer has spread, swollen lymph nodes under the arm (axillary lymphadenopathy) or signs of metastasis in other parts of the body may also occur.

Invasive Breast Cancer Treatment

Treatment options for invasive breast cancer depend on several factors, including the stage of the cancer, hormone receptor status, HER2 protein levels, genetic mutations and the patient’s overall health.

In general, early-stage breast cancer (Stages 1 to 3) is often treated with a combination of surgery, radiation therapy and drug therapies. Breast cancer surgery might involve removing the tumor (lumpectomy) or the entire breast (mastectomy), while radiation therapy for breast cancer helps target any remaining cancer cells.

Many patients also receive chemotherapy for breast cancer or other drug treatments before (neoadjuvant) or after (adjuvant) surgery. These treatments might include hormone therapy if the cancer is hormone receptor-positive or targeted drugs like those used for HER2-positive cancers. The goal is to reduce the risk of the cancer coming back.

For patients with more advanced or metastatic breast cancer (Stage 4), the focus shifts to chemotherapy, hormone therapy, targeted drugs or sometimes immunotherapy. These treatments aim to control the cancer’s spread and manage symptoms. Surgery and radiation therapy may still be helpful in specific cases.

Invasive Breast Cancer Care at City of Hope

At City of Hope, each treatment plan for invasive breast cancer is personalized based on the state-of-the-art therapies available and is aligned with the patient’s individual needs and preferences.