Lobular carcinoma in situ (LCIS) is a noninvasive carcinoma that involves clusters of cells proliferating in the lobules. If there is invasion of the ducts or basement membrane, LCIS has progressed to invasive lobular carcinoma (ILC).
LCIS does not involve basement membrane infiltration and as such is rarely associated with microcalcifications or stromal reactions, which produce densities visible on mammography.
LCIS involves a loss of E-cadherin, a cellular adhesion transmembrane protein that aids in the adhesion of epithelial cells of the breasts. It is thought that E-cadherin functions as a tumor suppressor protein and is lost as a result of a gene mutation in CDH1. These cancerous cells have no attachment to adjacent cells (i.e. loosely cohesive). Mucin-positive signet ring cells can also be present in LCIS.
As LCIS does not invade the surrounding tissue (i.e. basement membrane), it is therefore not associated with the classic symptoms of breast cancer. Namely, there are no palpable masses and it is often discovered as an incidental finding while examining another lesion (e.g. fibroadenoma).
Patients with LCIS will require life-long surveillance due to the increased risk of breast cancer being present in both breasts. This is different from DCIS, which has an increased risk only in the affected breast.
LCIS involves life-long surveillance along with the consideration of chemotherapy in order to act as a preventative measure.
Treatment of LCIS can also involve prophylactic bilateral mastectomy. This is especially relevant for those with a family history of breast cancer, BRCA mutations, and/or those patients who choose to forgo chemotherapy.
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