Lobular Carcinoma In Situ (LCIS) is not an invasive cancer. It involves abnormal cell growth confined to the breast’s milk-producing glands. LCIS is considered a risk indicator rather than a form of breast cancer itself. Understanding this condition, how it is detected, and the associated risks is crucial for appropriate management.
Defining Lobular Carcinoma In Situ
LCIS is a condition where abnormal cells proliferate within the breast’s lobules, the small sacs responsible for milk production. The term “in situ” means the abnormal cells are entirely contained within the lobule’s lining. Because the cells remain confined, LCIS cannot spread to other parts of the body, which is the defining characteristic of invasive cancer. For this reason, LCIS is classified as a high-risk lesion or a marker of increased future risk for developing invasive breast cancer, not a true cancer.
Subtypes of LCIS
There are recognized subtypes of LCIS based on how the cells appear under a microscope. Classic LCIS involves cells that are smaller and relatively uniform in size. Other types, such as pleomorphic and florid LCIS, involve cells that are larger and appear more abnormal. These subtypes are sometimes viewed as being biologically more advanced and may warrant a more aggressive management approach than classic LCIS.
How LCIS is Detected
LCIS is almost always an incidental finding because it typically does not produce a lump detectable during a physical exam. Classic LCIS usually does not show up as a distinct mass or calcification on routine screening mammograms or ultrasounds. The condition is often multifocal, affecting multiple lobules, and is frequently bilateral.
The diagnosis is most commonly made by a pathologist examining tissue removed during a core needle biopsy performed for another reason. This might be a biopsy for microcalcifications or a suspicious area seen on imaging. The discovery of LCIS on a core biopsy may sometimes lead to a recommendation for a surgical excisional biopsy to ensure no more aggressive lesions, such as invasive cancer, are nearby.
Understanding the Risk Associated with LCIS
LCIS is recognized as one of the strongest identifiable risk factors for the later development of invasive breast cancer. Women with this diagnosis have an estimated risk of developing invasive breast cancer that is approximately 7 to 12 times higher than the general population. This translates to a cumulative lifetime risk that can range up to 25% to 30%.
The increased risk is not confined to the breast where the LCIS was originally found. LCIS is considered a systemic marker, increasing the risk of developing cancer in both breasts equally. Subsequent invasive cancers can be either invasive ductal carcinoma or invasive lobular carcinoma. While classic LCIS carries an elevated risk, the pleomorphic and florid subtypes are thought to confer an even higher risk for progression to invasive disease.
Management and Surveillance Options
Following an LCIS diagnosis, management typically centers on three main strategies: enhanced surveillance, chemoprevention, and, in select cases, surgical intervention.
Enhanced Surveillance
Enhanced surveillance involves rigorous monitoring to detect any developing cancer at the earliest possible stage. This generally includes an annual mammogram and a clinical breast examination every six to twelve months. Supplemental imaging with an annual breast Magnetic Resonance Imaging (MRI) is often recommended, especially for women with dense breast tissue or other risk factors. The goal is to catch any future invasive cancer when it is small and most treatable.
Chemoprevention
Chemoprevention involves taking medications to reduce the overall risk of developing breast cancer. Options include anti-estrogen drugs like tamoxifen, suitable for both pre- and postmenopausal women, or raloxifene, used for postmenopausal women. These medications can significantly lower the risk of developing estrogen receptor-positive breast cancer.
Surgical Intervention
For women with extremely high-risk factors, such as a strong family history or a known genetic mutation (e.g., BRCA1 or BRCA2), a prophylactic bilateral mastectomy may be considered. This surgical option removes both breasts to dramatically reduce the risk of developing future breast cancer. This is a highly personal decision and is not the standard recommendation for most women with classic LCIS.