Breast cancer in situ

Last reviewed: June 2020

Last updated: March 2020

Breast cancer in situ comprises ductal carcinoma in situ (DCIS), a noninvasive breast cancer that is confined to the duct in which it originates, and lobular carcinoma in situ (LCIS), a neoplastic proliferation of cells that is a risk factor for invasive breast cancer.

Typically asymptomatic and diagnosed at screening.

Breast cancer guideline recommendations differ on when to start screening and screening frequency. In the US, recommendations for bilateral mammography screening in average-risk women range from yearly starting at age 40 years (National Comprehensive Cancer Network) to every 2 years starting at age 50 years (US Preventive Services Task Force).

Diagnosis is with mammography, supplemented with other imaging, such as ultrasound or magnetic resonance imaging, and biopsy.

Chemoprophylaxis (e.g., with tamoxifen, raloxifene, or an aromatase inhibitor [anastrozole or exemestane]) can be used in high-risk patients. Some high-risk patients may choose to undergo preventive bilateral total mastectomy.

Treatment is usually lumpectomy (breast conserving surgery) followed by radiation therapy.

Definition

Breast cancer in situ is a noninvasive breast cancer that is confined to the duct or lobule in which it originated and does not extend beyond the basement membrane. The cancer does not have access to distant spread through lymphatics or the bloodstream. Ductal carcinoma in situ (DCIS) is a potential precursor of invasive carcinoma and suggests that cancer will become invasive at that site.[1] com.bmj.content.model.Caption@4c10ef87 [Figure caption and citation for the preceding image starts]: Ductal carcinoma in situFrom the private collection of Dr Sauter; used with permission [Citation ends].

Lobular carcinoma in situ (LCIS) develops in breast lobule(s) and/or terminal ducts and is usually found incidentally. Whereas DCIS predicts an increased risk of invasive ductal carcinoma developing at the site of a biopsy demonstrating DCIS, LCIS implies increased risk of invasive ductal or lobular carcinoma developing in either breast.[2] LCIS is not cancer but a pathologic description of a neoplastic proliferation of cells within lobules and/or terminal ducts, which is a risk factor for invasive breast cancer.[3] A finding of LCIS does not imply that cancer will form at the diagnostic site. Consequently, treatment for LCIS is less formalized than for DCIS. com.bmj.content.model.Caption@67e2df04 [Figure caption and citation for the preceding image starts]: Lobular carcinoma in situFrom the private collection of Dr Sauter; used with permission [Citation ends].