Millions of women across the globe are diagnosed with breast cancer every year. The World Cancer Research Fund and the American Institute for Cancer Research notes that more than 2 million new cases of breast cancer were diagnosed in 2018, making the disease one of the most commonly occurring cancers in the world.

Upon receiving a breast cancer diagnosis, patients typically have a number of questions, including which type of breast cancer they have. The American Cancer Society notes that there are many types of breast cancer, though some are more common than others. Learning to distinguish between the more common types of breast cancer, which include invasive ductal carcinoma, ductal carcinoma in situ and invasive lobular carcinoma, can help patients and their support teams better understand this difficult, yet beatable disease.

What are carcinomas?

The ACS reports that most breast cancers are carcinomas. Carcinomas are tumors that start in the epithelial cells that line organs and tissue throughout the body. Carcinomas can spread to other parts of the body, even though they do not always do so.

Invasive ductal carcinoma

Sometimes referred to as “IDC,” invasive ductal carcinoma accounts for between 70 and 80% of all breast cancers, making it the most common type of the disease, according to the National Breast Cancer Foundation, Inc.®. Invasive means the cancer has spread from the milk ducts, where IDC originates, to the surrounding breast tissues.

Ductal carcinoma in situ

Ductal carcinoma in situ, or DCIS, is a noninvasive breast cancer that starts inside the milk ducts. BreastCancer.org notes that “in situ” means the cancer is still in its original place, not having spread beyond the milk duct to any surrounding breast tissue. That’s helpful to know, as it calms patients’ fears knowing the cancer has been caught before it could metastasize, or spread. One out of every five new breast cancer cases is DCIS. While that might sound alarming, BreastCancer.org notes that DCIS incidence rates are possibly so high because people are living longer than they used to (a person’s risk for breast cancer increases with age) and education about breast cancer screening appears to be working, compelling more women to get mammograms.

Invasive lobular carcinoma

The ACS notes that roughly 10% of all invasive breast cancers are invasive lobular carcinomas, or ILC. The word “lobular” means that the cancer began in the lobules, which produce milk and empty out into the ducts that carry milk to the nipple. When a person is diagnosed with ILC, that means the cancer has broken through the wall of the lobule and has started invading the tissues of the breast. Over time, ILC can spread to the lymph nodes and possibly even other areas of the body.

The type of breast cancer a person has will affect his or her treatment. As prevalent as breast cancer may seem, it is beatable, and many people overcome the disease and go on to live happy, full lives.