A breast cancer diagnosis brings many questions, and one of the first things to understand is the type of cancer involved. Not all breast cancers are the same — they differ in how they grow, where they start and how they respond to treatment. Understanding these differences can help patients feel more informed and confident as they navigate their care.

This article highlights the main types of breast cancer, what makes each one distinct and why accurate diagnosis is essential.

How breast cancer types are classified

Breast cancer occurs when cells in breast tissue begin growing uncontrollably. While that may sound straightforward, the reality is more complex. Different types of breast cancer behave in unique ways, which is why medical teams work carefully to identify the specific type. This knowledge guides treatment plans and helps predict how well therapies may work.

Before diving into specific types, it’s helpful to understand how doctors classify breast cancer. Breast tissue includes different areas — the ducts that carry milk, the lobules that produce milk and the surrounding tissues. Cancer can begin in any of these areas, and its origin influences how it’s named and treated.

Doctors also assess whether cancer cells have remained in their original location or spread to nearby tissues. The distinction between “in situ” (staying in place) and “invasive” (spreading) cancer significantly affects treatment and outcomes.

Additionally, breast cancers are tested for specific proteins and receptors on their surface. These molecular characteristics help determine which treatments will be most effective, making accurate identification critical to care.

Ductal carcinoma in situ

Ductal carcinoma in situ, or DCIS, accounts for about 20-25 percent of breast cancer diagnoses. The name reflects the condition: abnormal cells are found inside the milk ducts but haven’t spread to surrounding tissue. Many medical professionals consider DCIS precancer because the cells haven’t become invasive.

DCIS typically doesn’t cause noticeable symptoms. Most cases are discovered through mammograms, which can detect calcium deposits often associated with DCIS. This is one reason regular mammography screening is so valuable — it can catch changes before they progress.

While DCIS isn’t life-threatening, it requires treatment because it can develop into invasive cancer if left untreated. Treatment usually includes surgery to remove the abnormal area, sometimes followed by radiation therapy to reduce the risk of recurrence. The approach depends on factors such as the size of the affected area and how the cells appear under a microscope.

The prognosis for DCIS is excellent, with cure rates near 100 percent when treated properly. However, women with DCIS have a higher risk of developing invasive breast cancer later, making ongoing monitoring with mammograms and clinical exams important.

Invasive ductal carcinoma

Invasive ductal carcinoma, or IDC, is the most common type of breast cancer, accounting for about 80 percent of diagnoses. IDC begins in the milk ducts but breaks through the duct walls and spreads into surrounding tissue. From there, it can reach lymph nodes and other parts of the body.

IDC can present in various ways. Some women discover a lump during self-examination, while others notice changes in breast shape, skin texture or nipple appearance. Sometimes IDC is found on routine mammograms before symptoms develop, which often leads to better outcomes.

The characteristics of IDC vary widely. Some tumors grow slowly and remain localized, while others are more aggressive. Medical teams perform several tests to understand each case, including examining tumor cells under a microscope and testing for hormone receptors and other proteins.

Treatment typically involves surgery — either a lumpectomy to remove the tumor and surrounding tissue or a mastectomy to remove the breast. Many patients also receive chemotherapy, radiation therapy or hormone therapy, depending on the cancer’s characteristics and stage.

Invasive lobular carcinoma

Invasive lobular carcinoma, or ILC, begins in the milk-producing lobules and spreads to nearby tissue. It accounts for about 15 percent of invasive breast cancers and has unique characteristics.

ILC tends to grow in a single-file pattern through breast tissue, which can make it harder to detect than IDC. It may not form a distinct lump and instead cause thickening or fullness in the breast. Because of this subtle presentation, ILC may be more advanced when discovered.

Mammograms may miss ILC more often due to its growth pattern. Additional imaging tests, such as MRIs or ultrasounds, are sometimes needed to evaluate its extent. Some women with ILC undergo more comprehensive imaging during diagnosis and treatment planning.

Treatment approaches for ILC are similar to those for IDC, but surgical planning may be more complex. Because ILC can be difficult to visualize, surgeons must be especially careful to remove all cancer while preserving healthy tissue.

Triple-negative breast cancer

Triple-negative breast cancer, or TNBC, is named for what it lacks — it doesn’t have receptors for estrogen, progesterone or the HER2 protein. This absence makes TNBC distinct from other types of breast cancer.

TNBC accounts for about 10-15 percent of breast cancers. It’s more common in younger women, particularly those under 40, and is more frequently diagnosed in African American and Hispanic women, as well as those with BRCA1 gene mutations.

TNBC tends to be more aggressive than hormone receptor-positive cancers. It often grows and spreads quickly and is more likely to recur within the first few years after treatment. However, TNBC often responds well to chemotherapy, and when it does, outcomes can be favorable.

Treatment options for TNBC have expanded in recent years. While hormone therapy and HER2-targeted drugs aren’t effective, newer treatments — including immunotherapy and PARP inhibitors — have shown promise for certain patients.

The importance of accurate diagnosis

Understanding the specific type of breast cancer is essential, as it directly influences treatment, prognosis and follow-up care. The diagnostic process involves imaging, biopsies and advanced pathology tests to identify the cancer type and its characteristics. This detailed information allows medical teams to personalize treatment for the best possible outcome.

Early detection saves lives

Early detection significantly improves breast cancer outcomes, making treatment more effective and less intensive. Regular mammograms are the most reliable method, with annual screenings recommended starting at age 45, or optionally at 40.

Learning about breast cancer is a vital step toward early detection and better long-term outcomes. This October, take the opportunity to educate yourself on breast cancer risk factors and explore available screening options. Maxim Healthcare offers comprehensive home health and care services to support individuals managing the challenges of cancer. Visit our locations page to connect with your local office and access the care you deserve.