A troubling trend is emerging in women’s health: a type of breast cancer that is harder to spot, slower to reveal symptoms — yet growing faster than any other. New research published in Cancer, the journal of the American Cancer Society, shows that invasive lobular carcinoma (ILC) — the second most common type of breast cancer — is rising three times faster than all other breast cancers combined in the United States.
Between 2012 and 2021, cases of ILC increased by about 2.8% each year, while other breast cancers rose by only 0.8%. This elusive form now accounts for more than one in ten breast cancer diagnoses nationwide, yet it often escapes detection in routine mammograms.
To understand what’s driving this rise and what women can do to protect themselves, we spoke with Dr. Leana Wen, CNN wellness medical expert and an adjunct associate professor at the George Washington University.
What Exactly Is Invasive Lobular Carcinoma?
“Invasive lobular carcinoma starts in the milk-producing glands — called lobules — and spreads into nearby breast tissue,” Dr. Wen explained. “It’s typically hormone receptor-positive, meaning the cancer cells grow in response to estrogen or progesterone.”
According to the National Cancer Institute, ILC is diagnosed in roughly 47,500 American women each year. While it’s less common than invasive ductal carcinoma (IDC), it still affects more women annually than cancers of the brain, kidney, liver, pancreas, or ovaries.
What makes ILC particularly challenging is how it behaves: instead of forming a firm, easily felt lump, it grows in thin, branching lines, blending almost seamlessly into normal tissue.
Why It’s So Hard to Detect
Unlike most breast cancers that appear as distinct masses on imaging scans, ILC’s subtle growth pattern makes it notoriously difficult to identify.
“This cancer tends to grow in single-file strands, slipping between healthy cells rather than pushing them aside,” said Dr. Wen. “That means mammograms — which rely on structural changes — may not catch it.”
As a result, mammograms can look deceptively normal even when cancer is present. Many women with ILC don’t feel a defined lump, leading to later diagnoses and more advanced stages by the time it’s discovered.
The Role of Advanced Imaging
Because standard mammograms can miss these tumors, additional imaging can help.
A breast ultrasound can detect thickened or abnormal tissue, while a breast MRI can provide a clearer picture, especially for women with dense breasts or a family history of breast cancer.
“Mammography is still the best screening tool for most women,” Dr. Wen emphasized. “But for those at higher risk, doctors may recommend supplementing it with ultrasound or MRI for greater accuracy.”
Who Is Most at Risk?
The new data show ILC rates rising across all racial and ethnic groups, but the sharpest increase — 4.4% annually — was among Asian American and Pacific Islander women.
Age also plays a critical role. Nearly 70% of new cases occur in women 60 and older, and the median age of diagnosis is 66.
“Women over 65 are more likely to be diagnosed with lobular than ductal breast cancer,” Dr. Wen noted. “Hormonal changes after menopause are a key driver, but lifestyle factors also matter.”
Why Are Cases Rising So Fast?
Researchers point to a combination of biological, hormonal, and societal factors behind the spike.
ILC is strongly hormone-linked, so any shift in hormone exposure — from postmenopausal hormone therapy to changes in reproductive timing — can influence risk. Meanwhile, obesity, alcohol consumption, and later childbearing have all been associated with an elevated risk of hormone-sensitive cancers.
“Better diagnostic awareness also plays a role,” Dr. Wen said. “In the past, some lobular cancers might have been misclassified as ductal cancers. Improved imaging and pathology mean we’re recognizing them more accurately today.”
The growing number of older women living longer after menopause adds another dimension — as the population ages, cases are expected to continue climbing.
Treatment and Outlook
Treatment for invasive lobular carcinoma mirrors that of other breast cancers but requires tailored strategies.
Surgery — either lumpectomy or mastectomy — is typically followed by radiation therapy. Because most ILC tumors are hormone-sensitive, endocrine (hormone-blocking) therapy such as tamoxifen or aromatase inhibitors is a cornerstone of treatment.
Chemotherapy may be used for more advanced or aggressive cases. In recent years, targeted therapies — drugs that block specific cancer cell growth signals — have offered new hope for patients with metastatic disease.
Still, experts caution that ILC can be more resistant to treatment once it spreads beyond the breast. “It often carries a poorer prognosis in advanced stages,” Dr. Wen warned, “which is why early detection is absolutely vital.”
Steps Women Can Take to Reduce Risk
While genetics and age can’t be controlled, several modifiable lifestyle choices can help lower risk:
Limit alcohol to no more than one drink per day — or skip it altogether.
Maintain a healthy weight through regular exercise and balanced nutrition.
Quit smoking, which damages cells and increases cancer risk.
Eat a nutrient-rich diet with fruits, vegetables, whole grains, and lean proteins to reduce inflammation.
“Knowing your personal risk is the first step,” said Dr. Wen. “Talk with your doctor about when to start screening and whether you need additional imaging beyond mammograms.”
She also urges women to pay close attention to any unusual breast changes — thickening, swelling, nipple discharge, or new areas of fullness — and to seek medical advice right away.
“Even if your mammogram was normal, don’t ignore your intuition,” she added. “If something feels off, get it checked.”
A Call for Awareness
The rise of invasive lobular carcinoma underscores the need for more research and public awareness.
“This isn’t just another statistic,” Dr. Wen said. “It’s a reminder that breast cancer is not one disease. Each subtype behaves differently — and understanding those differences can save lives.”
As scientists work to better understand ILC’s unique biology, one message remains clear: early detection saves lives.
With more precise screening, lifestyle awareness, and proactive medical care, women can stay one step ahead of a cancer that too often hides in plain sight.