Because lobular breast cancer (LBC) is a type of breast cancer that can be difficult to detect and challenging to treat, it is the focus of a special program at Memorial Sloan Kettering Cancer Center (MSK). Also called invasive lobular carcinoma, it is the second most common breast cancer.
“LBC is a kind of breast cancer that has its own unique features, which require a different approach to screening, diagnosis, and treatment,” says MSK breast oncologist Sherry Shen, MD.
Dr. Shen, MSK breast surgeon Anita Mamtani, MD, and MSK breast pathologist Fresia Pareja, MD, PhD, co-direct the new Lobular Breast Cancer Program at MSK. Their goals are to improve outcomes for people with LBC and to conduct more research into the biology of the disease.
Drs. Shen and Mamtani answer common questions about lobular breast cancer and discuss essential differences in diagnosis and treatment.
What is lobular carcinoma?
Lobular breast cancer accounts for 10-15% of all breast cancers. The American Cancer Society (ACS) estimates that over 33,000 women are diagnosed with LBC each year in the US. If ranked separately, LBC would be the seventh most common cancer among women in the US.
The ACS also reports that the incidence of LBC increased more steeply than all other types of breast cancer combined from 2012 to 2021, underscoring how important it is to find the best methods to diagnose and treat the disease.
The most common type of breast cancer is invasive ductal carcinoma, or ductal breast cancer (DBC). It accounts for nearly 80% of breast cancer cases. You may also hear the technical term for this type of breast cancer, called “invasive carcinoma of no special type,” which is sometimes abbreviated to “NST.”
How does invasive lobular breast cancer differ from ductal breast cancer?
The biggest difference is in the symptoms and growth patterns:
- Invasive lobular carcinoma (ILC) cells don’t stick together and form a tumor like DBC and other breast cancers.
- Instead, they tend to grow in a line, in sheets, or as scattered cells that aren’t attached to one another.
What are the symptoms of lobular carcinoma?
“People with lobular breast cancer might feel a vague sensation, fullness, engorgement, or firmness in their breasts, or notice redness, skin or nipple changes, or discharge from the nipple,” Dr. Mamtani says. “Those are the most common signs in patients with an advanced lobular breast cancer that’s been hiding in their breast for a long time.”
In contrast, ductal breast cancer often forms a lump that’s visible on a screening mammogram and sometimes felt during a breast exam.
The symptoms of invasive lobular breast cancer include changes to these areas:
- Skin: dimpling or puckering, redness
- Breast: change in shape or size; new area of hardness, fullness or swelling
- Nipple: pulling to one side, inversion, discharge
Dr. Shen says: “If you have any of these symptoms, but standard mammogram imaging doesn’t show anything, don’t let it go. Be persistent and talk to your doctor. You may require an ultrasound in addition to a mammogram, or you may want to get a second opinion — particularly for younger women.”
When LBC is caught early, most people will have had no symptoms, Dr. Mamtani adds.
How is invasive lobular carcinoma detected?
“LBC is harder to detect because it grows in a way that’s not cohesive, so people are less likely to feel a mass or nodule, and it’s not easily seen on screening mammograms,” says Dr. Shen. “As a result, some people are diagnosed at a later stage when the tumor is bigger.”
“Lobular breast cancers are sneaky,” Dr. Mamtani adds. “Both their size and lymph node involvement tend to be notoriously underestimated on scans and during breast exams.”
This means that a tumor may be larger and that the cancer may have spread to more lymph nodes than initially seen on mammography.
How does MSK diagnose Invasive Lobular Breast Cancer?
The screening tools MSK uses in addition to mammography to accurately diagnose ILC include ultrasound, contrast enhanced mammogram, and MRI. However, those tests aren’t typically ordered until symptoms are reported or a suspicious area is detected during breast cancer screening.
With appropriate screening, most lobular carcinomas can still be detected at an early stage.
How is lobular carcinoma treated?
Treatment guidelines for LBC are often based on research done in people with DBC. Recognizing the need to refine treatment approaches for LBC was a key reason MSK created the new program.
“We treat our patients using the latest imaging technology, surgical techniques, radiation and drug therapies, and clinical trials,” Dr. Shen says. “We know each case is different, and our experts will make sure people with LBC get the most specialized and up-to-date care.”
Currently, LBC that has spread and progressed to stage 4 is treated similarly to DBC.
Stage 4 breast cancer requires treatment with oral medications or intravenous therapies that go through the whole body to target breast cancer cells wherever they are. Treatment needs to be ongoing to shrink the cancer and keep it under control.
“This is where there’s a lot of innovation happening,” Dr. Shen says. “There’s an urgent need to develop new treatments that improve upon our standard of care.”
What genetic mutations are important in lobular breast cancer?
Identifying the genetic makeup of tumors, including mutations that may be driving the cancer, can help doctors select the best treatment. Researchers have discovered that lobular breast cancer has different gene mutations than ductal breast cancer.
- Some gene mutations, like in the CDH1 gene, are unique to LBC
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Other genetic mutations are found in greater frequency in LBC than in DBC, including:
- PIK3CA
- AKT1
- ERBB2 (HER2)
- This is especially important in stage 4 disease because certain treatments have been developed to target specific mutations.
MSK uses a genetic test called MSK-IMPACT® to find mutations and other critical changes in tumors that other tests can miss. Doctors can quickly find out whether a cancer will respond to certain treatments.
Is the prognosis for lobular carcinoma similar to other types of breast cancer?
“There are several factors that go into prognosis,” Dr. Shen says.
A major factor is the stage at diagnosis. The lower the stage, the less likely the patient will have a recurrence. Stage 3 has the highest risk of the cancer returning. Lobular carcinoma can recur much later than the ductal type, often many years after the primary diagnosis.
Where in the body does invasive lobular breast cancer spread?
When LBC affects areas of the body outside the breast, the biology and spreading pattern are unique. Because lobular cancer cells don’t tend to clump together, they can spread along the linings of organs, such as the ovaries, the uterus, the gastrointestinal tract, and even the lining of the brain and spinal cord. In contrast, ductal cancers don’t tend to spread to those organs and instead form distinct tumors.
A very small number of people — 5% or less — are initially diagnosed with stage 4 disease.
Is lobular breast cancer always invasive?
According to Dr. Mamtani, there is no such thing as “noninvasive cancer.”
“Cancer is, by definition, an invasive process capable of spreading and moving through the breast and to other parts of the body,” she explains. “The fact that a cancer is localized in the breast at the time of diagnosis doesn’t make it noninvasive. It means that it has been caught at an early stage, but still warrants prompt and comprehensive evaluation and treatment.”
What are the “in situ” growths in the breast that are noninvasive?
There are precancerous breast conditions found in the ducts, which are called “in situ” and are not invasive. For example, ductal carcinoma in situ (DCIS) is stage 0, with no potential to spread beyond the breast.
On the other hand, LBC that is diagnosed at stage 1, 2, 3, or 4 is invasive and requires treatment. A breast biopsy can determine whether a breast tissue sample contains precancerous or cancerous cells.
A number of noncancerous conditions grouped under the term lobular neoplasia, such as atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS), can raise a person’s risk for getting cancer.
“Lobular neoplasias are not a precursor to cancer,” says Dr. Mamtani. “We do not remove them, but it means that a person is at higher risk of getting breast cancer. They should be monitored with a good screening plan, and may be offered medications to reduce their risk of breast cancer.”
What are other subtypes of lobular carcinomas?
There are several subtypes of invasive lobular breast cancers, and MSK treats all of them. They include:
- Pleomorphic LBC, which is rare but considered aggressive. Its tumor cells are large, vary in size, and more actively divide.
- Invasive ductal carcinoma-lobular (IDC‐L) is a “mixed” version in which people have both DBC and LBC.
- Bilateral LBC, which occurs when people are diagnosed with LBC in both breasts. LBC has a slightly higher likelihood of developing in both breasts compared to DBC.
Why should people with lobular carcinoma come to MSK?
Because MSK’s breast cancer experts across all specialties — including surgeons, radiologists, radiation oncologists, pathologists, and medical oncologists — focus only on breast cancer, they’re able to work together to create personalized treatment options for every patient. This includes clinical trials that offer people with LBC the chance to access treatments that are not available at other hospitals.
“That’s another reason to come to MSK, especially if you have stage 4 lobular breast cancer,” says Dr. Shen. “We can do genetic testing of your cancer to learn what those unique genetic mutations are and use that information to possibly match you to clinical trials that will benefit you most.”
Dr. Shen adds, “There’s a different biology behind lobular breast cancer, and different genetic characteristics. As we develop new clinical trials specific to lobular breast cancers and their genetic profiles, we will learn how to treat them more precisely.”
Key Takeaways
- Lobular breast cancer is harder to detect because it grows differently than other breast cancers. Instead of forming a lump, the cancer cells grow in lines or sheets and spread out through the breast tissue. This makes it more difficult to see on mammograms and feel during exams, so doctors may need to use additional tests like ultrasounds or MRIs to find it.
- Lobular breast cancer is the second most common type of breast cancer. Research from the American Cancer Society show the incidence of this kind of breast cancer is growing more quickly than all other forms of breast cancer combined.
- The warning signs of lobular breast cancer are different from typical breast cancer symptoms. Rather than feeling a distinct lump, people might notice their breast feels full, firm, or swollen, or they might see skin changes, nipple discharge, or dimpling. If you notice any of these symptoms but a mammogram doesn’t show anything wrong, it’s important to keep asking questions and possibly get a second opinion.
- Lobular breast cancer has unique genetic mutations that affect treatment options. Scientists have found that lobular breast cancer has different gene changes than the more common ductal breast cancer, including mutations in genes like CDH1, PIK3CA, and AKT1. Understanding these genetic differences helps doctors choose the best treatments and match patients to clinical trials that target their specific type of cancer.
- When lobular breast cancer spreads, it behaves differently than other breast cancers. Because the cancer cells don’t stick together, they can spread along the linings of organs like the ovaries, stomach, intestines, and even the brain and spinal cord, rather than forming distinct tumors. The cancer can also come back many years after the original diagnosis, so long-term monitoring is important.