By Dr. Julie Lang
University of Kentucky
When most people hear the words “breast cancer,” they may think of just one disease. In reality, breast cancer is an entire family of diseases. Some begin in different parts of the breast, while others are defined by the genes, proteins and hormones that help cancer cells grow. These differences affect how a cancer behaves and which treatments are most likely to work.
Understanding the different types of breast cancer helps doctors choose the most effective treatment for each patient.
The more common types
Ductal carcinoma in situ, often called DCIS, begins in the milk ducts and has not spread outside the ducts. Because it is confined to its original location, it is sometimes referred to as Stage 0 breast cancer. DCIS is highly treatable and is often found through routine mammograms before symptoms develop.
Invasive ductal carcinoma (IDC) is the most common type of breast cancer. Like DCIS, it begins in the milk ducts, but it has spread into nearby breast tissue. IDC accounts for most breast cancer diagnoses and can vary in how quickly it grows and spreads.
Invasive lobular carcinoma (ILC) begins in the milk-producing glands, called lobules, and spreads into surrounding tissue. It’s the second most common type of breast cancer. Unlike many breast cancers, ILC may not form a distinct lump. Instead, it often grows in thin lines or sheets of cells, making it more difficult to detect with exams or imaging. It also occurs in both breasts more often than many other breast cancer types.
Receptor subtypes
In addition to where a cancer begins, doctors also classify breast cancers based on whether cancer cells have certain proteins, called receptors, that help them grow.
• Hormone receptor-positive breast cancer has proteins on its cells that allow hormones like estrogen or progesterone to fuel its growth. It’s the most common subtype of breast cancers, and it can usually be treated with medications that block the hormones so the cancer can’t grow.
• Another subtype is HER2-positive breast cancer. Patients with this type produce too much of the HER2 protein, which fuels cancer growth. This subtype can be more aggressive, but there are several therapies available that can target HER2 to treat the cancer.
• Triple negative breast cancer is an aggressive form of invasive cancer and the rarest of these subtypes. If a patient is negative for estrogen, progesterone and HER2 receptors (triple-negative), then the common treatments that use these receptors as targets will not work. Researchers are continuing to work on new treatment options for patients with this disease.
Rarer types of breast cancer
Most breast cancers fall into the categories above, but there are several other rare forms of the disease.
Inflammatory breast cancer is a rare but aggressive form of breast cancer that affects the skin and lymph vessels of the breast.
Unlike many breast cancers, it typically does not cause a lump. Instead, symptoms may include redness, swelling, warmth, itching or skin that looks thickened or dimpled, sometimes resembling an orange peel.
Paget disease of the breast is a rare cancer that affects the nipple and the surrounding areola.
Symptoms can resemble common skin conditions such as eczema and may include redness, itching, scaling, crusting or nipple discharge. Because the symptoms can seem harmless, some patients delay seeking medical attention.
Male breast cancer. Men have breast tissue, so they can develop cancer, too. There are no proven screenings for male breast cancer, so it’s important for men who notice unusual changes in breast tissue to speak to their doctor.
And there are still more — even rarer forms of breast cancer include medullary carcinoma, tubular carcinoma, phyllodes tumors, mucinous carcinoma, metaplastic breast cancer and angiosarcoma of the breast.
Why does knowing the type of breast cancer matter for the patient?
These cancer types behave differently. The type of breast cancer helps determine how quickly it may grow, what treatments are most likely to work and what a patient can expect from the treatment. Every patient is unique, and there is no one size-fits-all approach to treating this group of diseases. A treatment that works well for you may not work at all for a friend with a different type of breast cancer.
The good news is that many breast cancers can be found early through routine screening. Mammograms remain one of the most powerful tools for detecting breast cancer before symptoms develop, when treatment is often most effective. The UK Markey Cancer Center recommends beginning annual mammograms for women beginning at age 40.
Dr. Julie Lang, M.D., is a medical director for the Comprehensive Breast Care Center at the University of Kentucky Markey Cancer Center.