Lobular Breast Cancer Rates Rising Steeply in the U.S.

A relatively uncommon type of breast cancer is on the rise in people in the U.S., according to a new report by the American Cancer Society.

Over the last decade, new cases of invasive lobular carcinoma (ILC) have increased three times faster than all other breast cancers, across all races and ages. The uptick in ILC was even higher among Asian American and Pacific Islander women, with an increase of 4.4% per year from 2012 to 2021, and lowest for American Indian/Alaska Native women (2.5% increase). Researchers aren’t sure what’s contributing to this rise.  

Unlike the more common invasive ductal carcinoma, lobular breast cancer starts in the glands of the breast that produce milk, called the lobules. It can then spread into other areas of the breast if it’s invasive. Lobular breast cancer behaves differently than ductal breast cancer, including how it appears and grows. It’s also often difficult to see lobular breast cancer in mammograms, which may delay detection and lead to worse outcomes for people. 

“The reason lobular cancers are hard-to-see lumps is that they grow in straight lines instead of forming a mass,” said Maxine Jochelson, MD, who serves on the scientific advisory board for the Lobular Breast Cancer Alliance. 

The new report estimates that 33,600 women will be diagnosed with lobular breast cancer or ILC this year. 

“Although lobular breast cancer accounts for a little over 10% of all breast cancers, the sheer number of new diagnoses each year makes this disease important to understand,” said Angela Giaquinto, MSPH, a cancer surveillance researcher at the American Cancer Society and author of the report, in a press release. 

While survival for women diagnosed with ILC is slightly higher than for ductal breast cancer in the first seven years after diagnosis, survival rates beyond seven years are lower for ILC. This highlights “the pressing need for prevention and early detection strategies targeting this subtype to be brought to the forefront,” said Giaquinot. 

There’s not a lot of research specifically focused on lobular breast cancer, since lobular is normally grouped in with ductal breast cancer during research studies. Giaquinto and the other authors of the report say this needs to change to better understand the disease and improve long-term survival rates.