Literally meaning “in place,” the term “in situ” refers to a very early form of cancer.  In general, the term “in situ” is used to indicate that abnormal cancer cells are present but have not spread past the boundaries of tissues where they initially developed.   Lobular carcinoma in situ (LCIS) refers to a sharp increase in the number, appearance, and abnormal behavior of cells contained in the milk-producing lobules of the breast (found within the lobes).

Though categorized as a stage 0 breast cancer (the earliest stage), LCIS is not considered a cancer. Rather, it is “marker” (a signal) that breast cancer may develop. In fact, LCIS has recently been renamed lobular neoplasia to signify this belief.  Neoplasia is defined as an abnormal growth in the number of cells. Though LCIS is not considered a cancer, women who are diagnosed with LCIS (also called lobular neoplasia) are at a higher risk of developing breast cancer later in life.

According to the National Cancer Institute, a woman with LCIS has a 25% chance of developing some form of invasive cancer (either lobular, or more commonly, infiltrating ductal carcinoma) within her lifetime.

The number of women diagnosed with LCIS has increased in recent years, most likely due to more rigorous breast cancer screening and advances in mammography techniques.  Often, LCIS is encountered serendipitously (by chance) while a pathologist is examining tissue from a breast biopsy that was performed for another reason (for example, to examine an area of concern found by physical examination or with mammography).

Treating LCIS

Currently, the majority of women who have been diagnosed with LCIS do not receive treatment after biopsy.  Instead, they are closely monitored by physicians with frequent clinical breast exams and mammograms.  It is essential that women with LCIS examine their breasts carefully, once a month, and see a physician immediately if they notice any changes or abnormalities. 

Prophylactic Mastectomy

Some women with LCIS who are very concerned with developing breast cancer (such as those who also have a strong family history of breast cancer and/or a proven genetic mutation) opt for the preventive removal of both breasts, a procedure called a prophylactic mastectomy.  Research shows that prophylactic mastectomy markedly reduces a woman’s risk of developing breast cancer for those at high risk.  Prophylactic mastectomy may be followed by immediate or delayed breast reconstruction.

While a bilateral prophylactic mastectomy removes the majority of breast tissue and reduces the risk of developing breast cancer, it is impossible to remove every breast cell. Thus, it is still possible to develop breast cancer even if both breasts are removed. According to Lynn C. Hartman, MD of the Mayo Clinic in Rochester, Minnesota, if only three cells are left after a mastectomy, cancer could develop from those three cells.  In a study conducted by the Mayo Clinic, three of 214 women who had prophylactic bilateral mastectomies between 1960 to 1993 developed breast cancer and two of the women later died. 

Tamoxifen

The option of taking medication to reduce breast cancer risk is also available to women with LCIS.  In a large clinical trial conducted by researchers with the National Surgical Adjuvant Breast and Bowel Project (NSABP), 13,388 women who were at high risk of developing breast cancer were given either the drug tamoxifen or a placebo (sugar pill) to determine whether tamoxifen could lower the risk of breast cancer.  All of the women in the study had a history of LCIS and/or other risk factors for breast cancer (such as a family history or atypical hyperplasia, an abnormal increase in the number of breast cells, diagnosed by a previous breast biopsy).  The trial revealed a 49% decrease in the incidence of invasive breast cancer in women who were given tamoxifen in the study compared with women who took the placebo (sugar pill). 

As a result of the NSABP trial, the U.S. Food and Drug Administration (FDA) approved the use of tamoxifen for women at high risk of breast cancer.  Many women with LCIS take tamoxifen to help prevent breast cancer.  Women with LCIS are encouraged to discuss the possibility of taking tamoxifen with their physicians.

A second clinical trial by the NSABP called the STAR trial is currently underway.  The STAR is intended to compare the effectiveness of tamoxifen with raloxifene, a promising new drug that may help prevent breast cancer in women over age 35 who are at high risk for breast cancer.  The STAR trial is still recruiting participants across the United States and Canada.  Many women with LCIS are eligible to participate in the STAR trial.  Several centers across the United States are participating in this trial.  Click here for more information on eligibility requirements and how to enroll in the STAR clinical trial.

Additional Resources and References

• The National Cancer Institute (NCI) provides information on LCIS at http://www.cancer.gov/
• The American Cancer Society provides information on LCIS at http://www.cancer.org/
• To learn more about LCIS and other types of breast cancer, please visit http://www.imaginis.com/breasthealth/breast_cancer.asp

Updated: September 12, 2007

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