A hard-to-spot breast cancer now makes up more than 1 in 10 cases in the US: Report

(NEW YORK) — A fast-rising form of breast cancer that’s harder to detect on mammograms now makes up more than one in ten cases in the United States, according to a new report from the American Cancer Society (ACS). 

Invasive lobular carcinoma, the second most common breast cancer type, is increasing about 3% each year, more than triple the rate of other breast cancers, the report, published on Tuesday morning, found.

About 80% of breast cancers are the invasive ductal type, which occurs when cancer cells grow in the milk ducts and invade the surrounding breast tissue.

However, incidence of invasive lobular carcinoma, a cancer than develops in the milk-producing glands of the breast — once rare — has doubled since the 1970s.

Lobular breast cancer hasn’t drawn much attention partly because many people view the five-year survival rate, which is over 90%, as a “cure rate,” but survival often drops after that point, Rebecca Siegel, an author of the report and senior scientific director of surveillance research at the ACS, told ABC News.

“And so, if you look at five-year survival, actually women with lobular breast cancer do better than ductal breast cancer,” she said. “I think that’s probably why it hasn’t gotten a lot of attention.”

However, Siegel added that the long-term outlook is poorer than for other breast cancer subtypes. 

“For metastatic disease, women with lobular breast cancer are about half as likely to be alive at 10 years,” she said.

Lobular cancers are rising even faster for women under 50, at more than twice the rate of other breast cancers, the report found.

The cancer is most common in white women, with about 14 cases per 100,000 — 33% to 55% higher than in other racial and ethnic groups — but the fastest rise, at nearly 4.5% a year, has been seen among Asian American and Pacific Islander women.

Diagnosing and treating lobular breast cancer differs from other types in several ways, Dr. Anita Mamtani, a surgical oncologist specializing in breast cancer at Memorial Sloan Kettering Cancer Center, told ABC News.

Mamtani explained that instead of forming a lump, “lobular cancers tend to grow in a straight line or sheet-like patterns.”

This growth pattern can make lobular tumors harder to spot on mammograms, Mamtani said. Patients tend to notice subtle changes such as breast fullness, firmness, swelling, skin redness, nipple changes or discharge.

Compared with other types of breast cancer, lobular cancers are also less responsive to some treatments and more likely to occur in both breasts, which may contribute to poorer long-term outcomes, according to the report.

However, lobular breast cancer still has a strong outlook when found early. The five-year survival rate for early-stage disease is about 99%, and overall survival across all stages is roughly 91%. Outcomes are even better for women who keep up with regular breast cancer screening.

“We will use a variety of diagnostic tools for most patients but, for lobular cancer, that arsenal will include not only mammograms but also ultrasound, contrast-enhanced mammograms, and MRIs,” Mamtani said. 

With proper screening, lobular cancer can often be caught in its early stages, she added.

Overall, breast cancer deaths have dropped 44% since 1989, but the disease still affects one in eight women and remains a leading cause of cancer death, according to the ACS. 

For all types of breast cancer, regular mammograms remain the best way to catch disease early. For women at average risk, the U.S. Preventive Services Task Force recommends screening every two years from ages 40 to 74.

Women who are at higher risk with a family history of breast cancer or other risk factors should discuss timing of screening with their health care provider.

Nearly half of uninsured women skip breast cancer screening because of cost concerns, the report noted. Free or low-cost options are available through the Centers for Disease Control and Prevention, the National Breast Cancer Foundation, the American Breast Cancer Foundation and local programs.

Experts also recommend maintaining a healthy weight, staying active, limiting alcohol and speaking with your doctor about personal risk factors.

Jamie Parkerson, MD, MS, is a fourth-year psychiatry resident and a member of the ABC News Medical Unit.

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