Lobular carcinoma in situ (LCIS)

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Definition

Lobular carcinoma in situ (LCIS) occurs within the lobules located at the end of the breast ducts. The term "in situ" means that the abnormal cells remain in place and don't spread beyond the lobule. LCIS is most often diagnosed in premenopausal women and found incidentally as a result of biopsies done for another reason, such as a suspicious breast lump or an abnormal mammogram. LCIS itself often doesn't show up on mammograms.

Most cancer experts don't consider lobular carcinoma in situ to be cancer. Rather, it's considered an area of abnormal tissue growth that signals an increased risk of developing invasive breast cancer later on. Best estimates put this risk at seven times — or more — that of the general population. The increased risk applies not only to the breast the LCIS is found in, but also to the other breast.

Researchers continue to explore whether in some cases lobular carcinoma in situ may actually be a preinvasive cancer, just like ductal carcinoma in situ.

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