Terminology Challenges

The terminology used to describe DCIS and LCIS is often inconsistent. Although medical authorities and organizations have rationales for their choice of descriptive terms defining DCIS, patients may find the variation among definitions confusing. Key points of commonality to reinforce:

• DCIS cells are abnormal and do have characteristics of cancer cells
• DCIS cells are contained within the basal membrane of terminal lobar ductal units (TDLU) and lactiferous ducts
• DCIS cells are non-invasive but may acquire the ability to breach the basement membrane and invade other tissues.

DCIS definitions:

• The National Cancer Institute (NCI) at the National Institute of Health (NIH) defines DCIS as "A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called ductal carcinoma in situ and intraductal carcinoma."
• The American Cancer Society defines DCIS as " the cancer cells are inside the ducts but have not spread through the walls of the ducts into the surrounding breast tissue."
• Breastcancer.org defines DCIS as "the most common form of non-invasive breast cancer."
• Cleveland Clinic defines DCIS as "a breast cancer which can grow within the milk duct, but does not invade into the surrounding tissue and does not spread to distant organs."
• College of American Pathologists defines DCIS as "DCIS is characterized by pre-cancerous or early-stage cell abnormalities in the breast ducts."
• Merriam-Webster Medical Dictionary "any of a histologically variable group of precancerous growths or early carcinomas of the lactiferous ducts that have the potential of becoming invasive and spreading to other tissues".
• MayoClinic.com "Ductal carcinoma in situ (DCIS) is considered the earliest form of breast cancer."
• Agency for Healthcare Research and Quality - "Ductal carcinoma in situ (DCIS) is noninvasive breast cancer that encompasses a wide spectrum of diseases ranging from low-grade lesions that are not life threatening to high-grade lesions that may harbor foci of invasive breast cancer. DCIS is characterized histologically by the proliferation of malignant epithelial cells that are bounded by the basement membrane of the breast ducts."

LCIS (Lobular Neoplasia) definitions

• The National Cancer Institute (NCI) at the National Institute of Health (NIH) defines LCIS as "A condition in which abnormal cells are found in the lobules of the breast. This condition seldom becomes invasive cancer. However, having LCIS in one breast increases the risk of developing breast cancer in either breast. Also called lobular carcinoma in situ.”
• The American Cancer Society defines LCIS as "a type of in-situ carcinoma of the breast. While DCIS is considered a pre-cancer, it is unclear whether LCIS is definitely a pre-cancer or if it is just a general risk factor for developing breast cancer. This is because LCIS rarely seems to turn into invasive cancer if it is left untreated. Women with LCIS do have a higher risk of getting breast cancer, but the cancer occurs just as often in the opposite breast (the one without any LCIS). Because it isn't clear if LCIS is a pre-cancer, many doctors prefer to use the term lobular neoplasia instead of lobular carcinoma in situ.
• Breastcancer.org defines lobular carcinoma in situ (LCIS) as an area (or areas) of abnormal cell growth but not a true breast cancer. LCIS is an indication that a person is at higher-than-average risk for getting breast cancer at some point in the future.
• MayoClinic.com “Lobular carcinoma in situ (LCIS) is an uncommon condition in which abnormal cells form in the milk glands (lobules) in the breast. LCIS is not cancer.”

As is evident from the above definition, LCIS is also sometimes called lobular neoplasia. Currently, lobular neoplasia is not considered an obligated precursor lesion meaning it will not ultimately turn into invasive cancer if untreated. LCIS is an indication or a risk factor that a person is at a higher risk of developing breast cancer in either breasts later on.

However, there is still some lingering doubt about LCIS not being a cancer precursor. In a 12 year follow up study of 180 women diagnosed with LCIS, found 9 women (5%) developed invasive breast cancer in the same breast with 8 of them having invasive lobular cancers. The researchers described LCIS as a more indolent form of in situ breast carcinoma when compared with DCIS (Fisher, et al., 2014).

Other studies (Lee, 2019) found incidences of both LCIS and invasive lobular cancer in the same breast. Since the pattern of mutation of both the LCIS and lobular cancer was similar, there is the suggestion the cancer evolved from the LCIS.

The pursuit of an accurate description of the ability of LCIS to become an obligate precursor lesion of invasive cancer is necessary to determine the best treatment protocols.

References:

Fisher, E. R., Land, S. R., Fisher, B., Mamounas, E., Linda Gilarski, L. & Wolmark, N. (2004). Pathologic Findings from the National Surgical Adjuvant Breast and Bowel Project Twelve-Year Observations Concerning Lobular Carcinoma In situ. Cancer. 100(2), 238-244.

Lee, J. Y., Schizas, M., Geyer, F.C., et al. (2019). Lobular Carcinomas In Situ Display Intralesion Genetic Heterogeneity and Clonal Evolution in the Progression to Invasive Lobular Carcinoma. Clin Cancer Res. 25(2), 674-686.

Reed, A., Kutasovic, J. R., Nones, K. et al. (2018). Mixed ductal-lobular carcinomas: evidence for progression from ductal to lobular morphology. The Journal of Pathology. 244(4), 460-468.

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