Epidemiology

It has been estimated that, in the US in 2024, there will be 56,500 new cases of ductal carcinoma in situ (DCIS) in women.[6]​ DCIS comprises approximately 85% and lobular carcinoma in situ (LCIS) is approximately 15% of in situ carcinomas of the breast.

The reported percentage of untreated cases of DCIS that will eventually progress to invasive disease varies widely, from 14% to 75%.[4] A diagnosis of LCIS confers an approximately 8- to 10-fold increased risk of breast cancer and the risk of invasive disease is equally distributed between both breasts.[7]

DCIS diagnosis peaks at age 70-74 years. Black, Hispanic, Chinese, and Korean women have a lower incidence of DCIS as compared with white women. The rate of diagnosis of DCIS in the US and in Europe increased dramatically through the 1990s due to the widespread use of mammography and has leveled off since. DCIS in men is uncommon, accounting for approximately 7% of all male breast carcinomas. Compared with invasive carcinomas of the breast, the prognosis associated with DCIS in men is excellent; however, clinical features, pathology, and treatment of this disease are not well defined in the literature.[8]

While it is well established that hormone replacement therapy (HRT) is associated with an increased risk of invasive breast cancer, there is not a similar association with HRT and DCIS.[9] The lack of association is consistent across five observational studies and one large randomized trial.[9]

The true incidence of LCIS is difficult to determine, with reports ranging from 0.07% to 3% in core biopsy specimens.[3] Multiple publications indicate that the incidence of LCIS is increasing, which may be attributed to better screening techniques, more core biopsies being carried out, and better recognition by pathologists. The incidence of LCIS increased from 0.9 in 100,000 person-years between 1978-1980, to 3.19 in 100,000 person-years from 1996-1998.[3][10] Analysis of the Surveillance, Epidemiology, and End Results (SEER) data showed that the incidence of LCIS increased from 2.00 in 100,000 in 2000, to 2.75 in 100,000 in 2009.[7]

SEER data from 18,835 women diagnosed with LCIS from 1990-2015 demonstrated that, compared to 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.[11]

Lobular carcinoma, both in situ and invasive, is rare in males, with an incidence of about 0.5% to 1%.[12][13]

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