Sharp rise in lobular breast cancer cases across US alarms health experts

Breast cancer awareness month 2025: Cases of invasive lobular carcinoma are increasing nearly three times faster than other breast cancers, raising alarm over detection, diagnosis, and treatment gaps

A new study has raised alarm over a surge in cases of a rare and aggressive form of breast cancer in the United States. Known as invasive lobular carcinoma (ILC), the cancer is hard to detect through routine screenings and is now being diagnosed more frequently among women.

Rates of lobular breast cancer are rising nearly three times faster than other breast cancer types, rising by 2.8 per cent each year compared to just 0.8 per cent, says the new research published in the journal Cancer. Although ILC had traditionally been seen as a more subtle subtype, this new trend is raising alarm bells about detection, treatment, and longer-term outcomes.

 

 

What is invasive lobular carcinoma (ILC)?

ILC is a form of breast cancer that begins in the lobules (milk-producing glands), rather than in the milk ducts (as is usual for the more common ductal cancers). Instead of forming a firm lump, ILC tumour cells often spread in a single-file or dispersed pattern, making detection by self-examination or even mammography more challenging.

 

Due to its unique nature, ILC can be more difficult to treat. It often responds less effectively to standard cancer therapies and tends to spread to uncommon sites such as the stomach, abdominal lining (peritoneum), and ovaries more frequently than ductal carcinoma.

 

“Although lobular breast cancer accounts for a little over 10 per cent of all breast cancers, the sheer number of new diagnoses each year makes this disease important to understand,” says Angela Giaquinto, lead researcher and associate scientist for cancer surveillance research at the American Cancer Society.

 

Also read: The cancers killing poor aren't being studied. WHO flags global trial gaps

 

Study findings: Increasing cases of ILC

• From 2012 to 2021, the incidence of ILC in the US rose by about 2.8 per cent each year, compared to only about 0.8 per cent annually for all other breast cancer types combined.
• Around 33,600 women in the US are expected to be diagnosed with ILC in 2025, making it the seventh most common cancer in women, with about 60 per cent more cases than ovarian cancer.
• While in early stages survival for ILC is comparable to ductal cancers, data show that once the disease spreads, long-term survival is poorer in ILC compared to more common types.

 

“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,” says Rebecca Siegel, senior author and senior scientific director, cancer surveillance research at the American Cancer Society.

 

According to the study Lobular Breast Cancer Statistics, 2025, this subtype is often grouped with the more common invasive ductal carcinoma in research and clinical trials, masking many unique and important characteristics, including how the cancer appears and grows. 

 

Rising risk: Who’s most affected by ILC?

About 56 per cent of ILC cases are found in women aged 65 and above, compared to 46 per cent for IDC (invasive ductal carcinoma). The average age at diagnosis is 66 years for ILC, versus 63 years for IDC.

 

Caucasian women have the highest rates of lobular breast cancer, with about 14.7 cases per 100,000, higher than any other racial or ethnic group. Across all groups, the risk increases steadily until ages 70–79, before starting to decline.

 

Researchers believe the rise in ILC, and breast cancer overall, is linked to changing lifestyle and hormonal factors. These include higher body weight, earlier onset of menstruation, later age at first childbirth, fewer children, later menopause, and increased alcohol intake in some groups.

 

Also read: Why more young people are being diagnosed with cancer than ever before

 

Limitations of the study

The study’s strength lies in its use of nationwide, population-based cancer registry data, offering detailed insights into a breast cancer subtype that is often under-researched. However, 

• The data could not account for comorbidities, screening behaviour, or lifestyle risk factors such as smoking.
• Mortality data was unavailable because death certificates do not record cancer subtype information.
• The study could not analyse different variants of lobular breast cancer, which may influence survival outcomes.
• Survival statistics were not adjusted for factors like tumour grade or treatment received.
• Findings were limited to first primary cancers, with no information on recurrence or long-term progression.