People with LCIS are considered to be at higher-than-average risk of developing invasive breast cancer over the next few decades of their lives. This is why doctors sometimes say that LCIS is a “marker” for increased breast cancer risk. The cancer can be either an invasive ductal carcinoma (cancer that starts in the duct and spreads beyond it) or an invasive lobular carcinoma (cancer that starts in the lobule and spreads beyond it). The invasive carcinoma may or may not develop from the original areas of LCIS that were found, and it can develop in either breast. Invasive ductal carcinoma is actually more common after LCIS than invasive lobular carcinoma is.
How greatly does having LCIS increase breast cancer risk? One estimate is that the lifetime risk of developing an invasive breast cancer is 30-40% for women with LCIS, versus a lifetime risk of 12.5% for the average woman. Another estimate suggests that an LCIS diagnosis increases breast cancer risk to 21% over the next 15 years.
If a woman with LCIS develops an invasive breast cancer, it doesn’t typically happen within a few years. Rather, it is more likely to happen over the long-term — in 10, 15, or 20 years or even beyond that. A woman with LCIS is considered to be at elevated risk for developing breast cancer for the rest of her life.
If you’ve been diagnosed with LCIS, learn what you can do to lower your risk of being diagnosed with an invasive breast cancer in the Lower Your Risk section.