October 15 is Global Lobular Cancer Awareness Day. Invasive lobular cancer (ILC) is breast cancer that begins in the lobules. ILC is an invasive breast cancer because cancer cells in the lobules have invaded nearby breast tissue and may travel from the breast to other parts of the body.
This type of breast cancer (ILC) is the second most common type of invasive breast cancer and tends to be hormone receptor positive (HR+), HER2-negative and slow growing. ILC is often hard to detect because of the way it grows. With ILC, cancer cells tend to form a single file line or a sheet, so a mass or lump may not be present.
“When cancer cells grow like this, it may be really hard to see them among normal breast tissue because they can just kind of hide in there,” said Megan Kruse, M.D., a breast medical oncologist at Cleveland Clinic. “Lobular can form a lump, it’s just less common. By the time they form those lumps, there’s a lot more cancer cells in the breast, and the cancer is more advanced at that point.”
Warning signs of ILC
While the warning signs of ILC are the same as for other breast cancers, Dr. Kruse shares more about why ILC may be harder to find on a mammogram than some other breast cancers.
“So many times we’re finding these cancers when they are a larger mass in the breast and a patient will notice that their breast feels heavy or a different size or the skin feels thickened, something a little bit different than the normal lump,” explained Dr. Kruse. “And then on screening mammograms, it can be really hard even for the best radiologist to detect them, because the findings for ILC are just a little bit less obvious than for other types of breast cancer.”
Identifying ILC
There are different imaging modalities used to look for breast cancer, including mammograms and breast MRIs (for women at higher risk), but ILC is not always readily visible on these types of tests. Other imaging tests in combination with mammography are under study for use in routine breast cancer screening that may help detect ILC.
Types of PET Scans
An FDG-PET scan measures the metabolic activity of a tumor. This type of scan may be used to look for metastatic breast cancer (MBC) and in some cases, to identify a breast cancer recurrence, but is not used as a screening test.
Because ILC is almost always HR+, a FES-PET scan may be used to look for estrogen receptor-positive (ER+) disease. The scan will ‘light up’ estrogen receptors in the cancer cells, making it easier to find recurrent lobular and metastatic lobular breast cancer. This may help doctors plan treatment.
Carissa’s ILC Story: Troubling Symptoms
In 2019, Carissa went in for her regular mammogram, during which her doctor noted that there might be something amiss with a lymph node in her breast. “At that point, they said it wasn’t really a big deal, they’d recheck it in six months,” Carissa recalled.
But a few months later, Carissa noticed the skin on her breast was changing. Then her breasts doubled in size. She went back to the doctor and had another mammogram and ultrasound, but nothing showed up. “They still thought it was lymph node, they didn’t know why this was happening,” Carissa said. “They did a skin biopsy and said it was fine. There were no masses. So once again, they said to keep an eye on it.”
Breast Cancer Diagnosis
In early 2020, Carissa had an MRI and an MRI-guided biopsy. “At that point, they said it was probably cancer, even though they couldn’t find anything,” she said. During this time, the PET scan Carissa had was a FDG scan, not an FES scan.
Carissa’s doctor recommended a bilateral mastectomy. During surgery, the surgical team discovered Carissa had ILC in her left breast and lymph nodes, and in her right breast.
Metastatic Breast Cancer
Then, in 2024, Carissa underwent a hysterectomy, which led to the discovery of cancer. A biopsy showed that Carissa’s cancer had spread to her ovaries and fallopian tubes. An FDG-PET scan showed no other signs of cancer.
Carissa was referred to another doctor for a second opinion. This doctor ordered an FES-PET scan. “It showed that in fact I still had some cancer cells in multiple other areas that the traditional PET scan could not detect,” Carissa said. She was diagnosed with metastatic breast cancer.
“When I had the regular FDG scan in 2020, it did show something on my ovaries that they thought was a narrowing of a vein,” explained Carissa. “But after the FES scan, I wonder if it wasn’t actually a string of cancer cells even back then.”
FES Moving Forward
Recently, the National Comprehensive Cancer Network updated guidelines for the use of FES-PET scans in certain circumstances to help identify recurrent lobular and metastatic breast cancer, which may help clinicians identify ILC.
“We may be able to able to better identify cancer cells using a scan like FES because the dye used for that study is specific for cells that have estrogen receptor so it finds lobular cancer cells, which almost always have estrogen receptor, better. The test isn’t perfect but it’s a great step forward,” Dr. Kruse explained. “Right now, this type of scan is only used for patients that we already suspect have spread of their cancer (metastatic disease) and not routinely when an ILC is first diagnosed. We hope that it will help better stage the cancer for patients earlier on in the evaluation but we aren’t using it there yet.”
Playing an Active Role
You play an active role in making treatment decisions by understanding your breast cancer diagnosis, your treatment options and possible side effects. Together, you and your health care provider can choose treatments that fit your values and lifestyle.
Statements and opinions expressed are that of the individual and do not express the views or opinions of Susan G. Komen. This information is being provided for educational purposes only and is not to be construed as medical advice. Persons with breast cancer should consult their healthcare provider with specific questions or concerns about their treatment.
