Although many of us think of breast cancer as a single disease, the diagnosis is not limited to one type. Most breast cancers start as small tumors. Some stay put; others travel. How the tumor behaves and how it grows will dictate how it’s classified and your treatment options.
The Cancer Treatment Centers of America website broadly organizes breast cancers into two groups based on how the cancer behaves: noninvasive (in situ) breast cancer and invasive (infiltrating) breast cancer.
Noninvasive Breast Cancers
In noninvasive breast cancer, “cancerous cells remain in a particular location of the breast, without spreading to surrounding tissue, lobules or ducts,” the website reports. Noninvasive breast cancers are generally earlier stage cancers that respond well to treatment. Ductal Carcinoma In Situ, or DCIS, is the most common form of noninvasive breast cancer; the American Cancer Society reports that 60,000 cases of DCIS, or about 20 percent of all breast cancer cases, are diagnosed in the United States each year.
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As the name implies, DCIS begins inside the milk ducts. The term “in situ” means that it stays within the duct and is considered noninvasive because it hasn’t spread to other surrounding tissues. Dr. Harold Burstein, institute physician at Dana-Farber Cancer Institute in Boston and associate professor of medicine at Harvard Medical School says it’s a “precancerous lesion, often diagnosed in women who’ve had mammograms, and it’s sort of a precursor to breast cancer.” He likens it to a colon polyp. “It’s a benign growth, but you remove it to remove the growth” and prevent the development of an invasive cancer.
Even with surgery to remove the growth, patients with DCIS are at higher risk of reoccurrence and later development of an invasive cancer, but Breastcancer.org reports the rate of reoccurrence is less than 30 percent.
Invasive Breast Cancers
In invasive breast cancers, “cancerous cells break through normal breast tissue barriers and spread to other parts of the body through the bloodstream and lymph nodes,” reports Breastcancer.org. According to the American Cancer Society, invasive ductal carcinoma, or IDC, is the most common form of breast cancer — about 80 percent of cancer diagnoses are IDC and about 180,000 new cases are diagnosed each year in the U.S.
As with DCIS, IDC also begins inside the milk ducts, but these growths have moved beyond those boundaries and have begun invading or infiltrating the tissues around the ducts. Unlike noninvasive lesions, these growths are cancerous tumors, and treatment will likely be more aggressive than with a DCIS diagnosis. If left untreated, IDC usually spreads to the lymph nodes and then onwards to other parts of the body.
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IDC Subtypes
There are five subcategories of relatively rare forms of IDC. These subtypes describe where exactly within the breast duct the tumor resides and what it looks like.
Tubular Carcinoma of the Breast: Usually small and shaped like tubes, these tumors tend to grow slowly and can look like normal cells. Although these cancers can arise in women at any age, the average age at diagnosis is mid-50s. Although it’s unclear exactly how prevalent this subtype is, estimates range from 8 to 27 percent of all breast cancers.
Medullary Carcinoma of the Breast: This rare type of slow-growing IDC gets its name from its appearance — as a fleshy growth that looks a bit like the medulla part of the brain. It tends to affect women in their late 40s or early 50s and is more common in patients with a BRCA1 mutation, a gene mutation that’s been linked to a higher incidence of breast cancer. Because it’s not as aggressive as some other forms of IDC, it’s generally easier to treat.
Mucinous Carcinoma of the Breast: Mucus lines the inside of our bodies, and that can create the right environment for mucinous carcinomas, which are also sometimes called colloid carcinomas. These rare tumors float in pools of mucus and tend to affect older patients in their 60s or early 70s. Because these cancers are insulated by mucus, they tend to spread to lymph nodes less easily and respond well to treatment.
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Papillary Carcinoma of the Breast: These rare cancers tend to affect older women who have already been through menopause. They usually have well-defined borders and finger-like projections, hence the name papillary. The Sidney Kimmel Comprehensive Care Center at Johns Hopkins University in Baltimore reports these cancers account for less than 1 percent of all breast cancers.
Cribriform Carcinoma of the Breast: These cancers invade the stroma, or connective tissues in the breast, and form twisted, nest-like structures. Breastcancer.org reports they can look like Swiss cheese, and about 5 or 6 percent of invasive breast cancer tumors contain cribriform structures.
Diagnosis Dictates Treatment
To further complicate matters, there are three other means of classifying breast cancers based on how they grow. Burstein explains that these different types of breast cancers are defined by diagnostic tests, such as biopsies, on “the tumor itself to characterize growth factor receptors in the cancer cell.”
Certain chemicals within the body can stimulate the growth of tumors, namely the hormones estrogen and progesterone and the protein human epidermal growth factor receptor 2, or HER2. Burstein says that when your doctor biopsies a tumor, he’s looking at which of these elements is causing your individual tumor to grow, and that information will dictate the course of treatment your doctor will pursue.
“We typically speak of three large groups of breast cancer. [The first is] estrogen receptor positive, which are also HER2 negative. [The second] group is called HER2 positive breast cancers, and of those, about half also express the estrogen receptors. And then there’s a group that lacks the estrogen receptor, the progesterone receptor and HER2, hence they call them triple negative.”
Dr. Melissa Pilewskie, a breast surgical oncologist at Memorial Sloan Kettering Cancer Center further explains via email that “the majority of breast cancers are positive for the hormone receptors [ER/PR] and negative for HER2, although a subset are HER2 positive or triple negative [negative for all three receptors].”
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What Are the Types of Breast Cancer? originally appeared on usnews.com
