Breast Cancer That's Harder to Detect Is on the Rise

 

• Invasive lobular carcinoma accounts for about 10% of breast cancer diagnoses.
• Its incidence is increasing at the rate of 2.8% annually -- more than triple that of other breast cancers combined.
• This cancer has unique characteristics that contribute to delayed detection, resistance to therapy, and poorer prognosis for advanced disease.

Invasive lobular carcinoma (ILC) now accounts for one in every 10 breast cancer cases in the U.S. and is increasing at more than triple the rate of other breast cancers, according to a report from the American Cancer Society (ACS).

In 2025, an estimated 33,600 women will be diagnosed with ILC, which has unique characteristics that make it more challenging to detect and can contribute to delays in diagnosis. If ranked as its own cancer, ILC would represent the seventh most common cancer diagnosed among women, according to a team of ACS researchers led by Angela Giaquinto, MSPH, writing in Cancer.

Incidence of ILC more than doubled over the past half century, growing from about 6 per 100,000 women in 1975 to 14 per 100,000 women in 2021. However, that rise escalated in the most recent decade of the study (2012-2021), with rates increasing by 2.8% per year compared to 0.8% for other breast cancers.

ILCs are more likely to be resistant to therapy compared with the most common subtype -- invasive ductal carcinoma -- and cases of advanced disease are associated with a poorer prognosis, according to the researchers.

"Invasive lobular breast cancer is very understudied, probably because of a very good short-term prognosis. But at 10 years, these women with metastatic disease are half as likely to be alive as their counterparts with ductal cancer, probably because of the unique spread and resistance to therapy," said co-author Rebecca Siegel, MPH, of the ACS, in a press release.

"Our study underscores the need for much more information on lobular cancers across the board, from genetic studies to clinical trial data, so we can improve outcomes for the increasing number of women affected with this cancer," added Siegel.

The study authors pointed out that ILC is typically combined with invasive ductal carcinoma in research and trials, masking many unique and important characteristics, including how the cancer appears and grows.

For example, ILCs grow in a linear or dispersed pattern -- instead of forming a lump typical of other breast cancers -- which makes it more challenging to detect clinically and through mammography, they noted. ILC can also have atypical symptoms such as "nipple inversion, skin thickening, or dimpling."

"The metastatic pattern of lobular carcinoma is also somewhat distinct, with a higher likelihood of spreading to the gastrointestinal and urinary tract lining and ovaries compared to [invasive ductal carcinoma]," wrote Giaquinto and co-authors. "Although lobular carcinoma prognosis is generally favorable, the disease is less responsive to neoadjuvant chemotherapy and may be at higher risk of bilateral involvement, late recurrence, and subsequent primary contralateral cancer."

The increasing incidence of ILC in the report was similar in women younger than age 50 (2.9% per year) and women 50 and older (2.8% per year), as well as in women of every racial and ethnic group. The trend was observed in localized and regional stage disease (increased rates of 3.9% and 1.4% per year, respectively), while the incidence of distant and unstaged disease was stable.

Giaquinto and co-authors said that the rising ILC incidence rates -- like those of other breast cancers -- are believed to be driven by risk factors such as obesity, younger age at first menstrual cycle, later age of first birth, later age at menopause, as well as increased alcohol consumption in some age groups.

For their study, the researchers used data from the North American Association of Central Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology, and End Results program to analyze incidence and outcomes of ILC by age, race, and ethnicity.

White women have the highest incidence rate of ILC (14.7 per 100,000 women), with Black women ranking second (11 per 100,000), but the steepest rise was observed among Asian American and Pacific Islander women, with an increase of 4.4% per year from 2012 to 2021.

Survival for women diagnosed with ILC was slightly higher than that for ductal breast cancer in the first 7 years after diagnosis (90.4% vs 89.7%) and comparable at 10 years. The 10-year relative survival with ILC was higher for localized disease, but lower for both regional (76.4% vs 78.2% for ductal carcinoma) and distant-stage disease (12.1% vs 19.6%, respectively).

"Distinguishing this breast cancer subtype from ductal carcinoma in research and clinical trials is increasingly important to help identify risk factors, facilitate treatment efficacy, and lead to better understanding of mechanisms of metastasis, all of which will improve outcomes for the increasing number of women diagnosed with this cancer subtype," wrote Giaquinto and co-authors.

Disclosures

Co-authors reported grants from the Breast Cancer Research Foundation, the Fashion Footwear Association of New York, and Genentech, Puma Biotechnology, Eisai, and Genentech/Roche, outside the submitted work.

Primary Source

Cancer

Source Reference: Giaquinto A, et al "Lobular breast cancer statistics, 2025" Cancer 2025; DOI: 10.1002/cncr.70061.

https://www.medpagetoday.com/hematologyoncology/breastcancer/117881