Epidemiology

It has been estimated that, in the US in 2025, there will be 59,080 new cases of ductal carcinoma in situ (DCIS) diagnosed in women.[10]​​ DCIS comprises approximately 85% of in situ carcinomas of the breast, with lobular carcinoma in situ (LCIS) accounting for most of the remainder.[11]

In the US, DCIS incidence peaks at ages 55-69 years.[12] DCIS incidence rates are influenced by breast cancer mammography screening uptake.[13][14]​​ The incidence rate of DCIS in the US and in Europe increased dramatically through the 1990s due to the widespread use of mammography. 

Among women attending breast cancer screening in the UK between 1988 and 2014, the overall risk of invasive breast cancer was 8.82 per 1000 women per year, and did not vary significantly with age at diagnosis of DCIS.[2]

A subsequent UK population-based cohort study (1990-2018) of women with non-screen-detected DCIS found an overall invasive breast cancer rate of 13.28 per 1000 women per year.[3] The following cumulative risks of invasive breast cancer by age at diagnosis were reported: 27.3% for <45 years, 25.2% for 45-49 years, 21.7% for 50-59 years, and 20.8% for 60-70 years.[3] Women diagnosed with non-screen-detected DCIS may present symptomatically (e.g., with interval DCIS between screening mammograms). Incidental diagnosis may be more prevalent among women who are younger at diagnosis, and who may not be eligible for screening.[3]

DCIS in men is rare, accounting for approximately 7% of all male breast carcinomas.[15]​ The prognosis associated with DCIS in men is excellent.[15][16]

Use of hormone replacement therapy is not associated with DCIS.[17] The lack of association is consistent across five observational studies and one large randomised trial.[17]

US Surveillance, Epidemiology, and End Results (SEER) data indicate that LCIS incidence increased from 2 cases per 100,000 in the year 2000 to 2.75 per 100,000 in 2009.[18]​ The increase may potentially be attributable to better screening techniques, more core biopsies being carried out, and improved recognition by pathologists.

US SEER data from 18,835 women diagnosed with LCIS from 1990 to 2015 demonstrated that, compared with white women, black women had a 30% higher risk of developing hormone receptor (HR)-positive breast cancer and an 85% higher risk of developing HR-negative breast cancer.[19]

Lobular carcinoma, both in situ and invasive, is rare in males, with an incidence of approximately 0.5% to 1.0%.[20][21]

Breast cancer in situ is principally screen detected. Mammography frequency is, therefore, a significant confounding factor in epidemiological studies.[14][22]​​

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