Lobular carcinoma in situ (LCIS) is a noninvasive precancer. Lobular means that the unusual cells are in the lobules, the parts of the breast capable of making milk. Even though LCIS contains the word carcinoma, which means "cancer," LCIS is not a cancer diagnosis. It is a diagnosis that means you are at increased risk of developing breast cancer.
Under the microscope, LCIS appears as a bunch of small, round cells stuffing the lobules, which normally don't contain any cells. (See diagram.)
If there are only a few cells and they're not too odd-looking, you have lobular hyperplasia. If they fill the whole lobule and look very atypical (odd), you have LCIS. We thought we understood the natural history of LCIS, but new information has challenged our previous ideas.
The old theory was that LCIS doesn't grow into cancer but signals a possible danger—the way, for example, an overcast day warns you it may rain. Because of this, many experts believed that LCIS wasn't, in fact, a true precancer but more of a risk factor. Recent studies, however, suggest that this may not be the case.
The first piece of evidence that LCIS can actually progress to invasive lobular cancer came from a 2004 analysis of 180 women who had participated in a study of the National Surgical Breast and Bowel Project. After 12 years of follow-up, the study showed that nine women (5%) developed invasive breast cancers in the same breast as the LCIS, and that eight of the nine (89%) were invasive lobular cancers — in the same area as the original LCIS.
A second piece of evidence was a study of women who had both LCIS and invasive lobular cancer in the same breast. The pattern of mutations in the involved cells was very similar, suggesting that one had indeed evolved from the other. More recently, molecular studies have shown that both LCIS and infiltrating lobular cancers are estrogen-receptor positive (ER+), HER2-negative, and lack expression of a protein called E- cadherin. (The E-cadherin protein helps cells stick together, and its absence may help explain why lobular cancers don't cling together in a nice lump but march cell by cell through the stroma in single file lines forming a diffuse pattern that is often difficult to detect.)
How is LCIS treated?
Still, LCIS is not cancer — and the vast majority of women diagnosed with LCIS will never get breast cancer. For this reason, LCIS doesn't call for an immediate decision. There is no rush to begin a treatment.
The National Comprehensive Cancer Network treatment guidelines recommend close follow-up for women with LCIS. If possible, this should be done at a program for high-risk women.These programs provide close follow-up, which means clinical breast exams every six months and yearly mammograms. That way if a cancer does develop, you're likely to catch it at an early stage and can decide then if you want to have a mastectomy or a lumpectomy and radiation.
Another option is to take tamoxifen or raloxifene (Evista) for five years to reduce your risk of developing breast cancer. Both drugs come in pill form and are taken daily. (Evista is an option only for postmenopausal women.) In women with LCIS, tamoxifen and Evista have been shown to decrease the chance of getting breast cancer by about 56%—which means 56% of the original risk. The risk of breast cancer for women with LCIS is 1% per year over that of the average woman, so taking tamoxifen or Evista would reduce your risk to 0.5% a year over that of the average woman. Since both drugs have side effects, you need to discuss the risks and benefits with your physician, as the risks may outweigh the benefit you would receive.
The most drastic option is bilateral prophylactic mastectomy. Why bilateral (both breasts)? Because if you have LCIS you have a risk of getting breast cancer in either breast, not just the breast in which the LCIS is found. Some women choose this because they want to know they've done everything they could. However, the reason this is considered drastic is that most women with LCIS will never go on to develop breast cancer.
If you have a family history of breast cancer in addition to LCIS and you want to understand more about whether your family history may contribute to your breast cancer risk, you should make an appointment with a genetic counselor to discuss testing for the hereditary breast cancer gene mutations, called BRCA1 and BRCA2, which put women at higher risk for breast and ovarian cancer. The National Cancer Institute and the National Society of Genetic Counselors can help you locate a genetic counselor near you. Under the Affordable Care Act, genetic counseling and testing are covered for high-risk women.
If you decide to have genetic testing and are found to carry a BRCA genetic mutation, it may influence your treatment decisions. If you have a BRCA gene mutation, your doctor may suggest that you consider a bilateral prophylactic mastectomy (removal of both breasts). This will reduce the chance of getting breast cancer by about 95%. The surgery is recommended if you have a strong family history of the disease. It is not recommended for women just because they have had a diagnosis of LCIS, however, some women do choose this option.
The most important thing to remember is that a diagnosis of LCIS is not an emergency and you should give yourself time to figure out what to do.