This page was reviewed under our medical and editorial policy by
Daniel Liu, MD, Plastic and Reconstructive Surgeon
This page was updated on October 18, 2022.
Invasive lobular carcinoma (ILC) is a type of invasive breast cancer, meaning the cancer has spread into surrounding breast tissue. ILC originates in the lobules, which are the part of the breast gland that produces milk. While it begins in the lobules, it has the potential to spread to other parts of the body through both the bloodstream and lymph nodes.
According to the American Cancer Society, ILC is the second-most common type of invasive breast cancer. ILC accounts for approximately 1 in 10 diagnoses of invasive breast cancer, while invasive (infiltrating) ductal carcinoma (IDC) accounts for 8 in 10. ILC most commonly affects both breasts.
Many symptoms of ILC are similar to those of other breast cancers. One difference is that part of the breast feels thicker than other parts. This is more common in ILC than a firm lump. Other ILC symptoms may include:
Changes to the nipple, skin dimpling and changes to the breast skin may also be symptoms of other types of breast cancer. Any unexplained changes to the body should always be discussed with a doctor.
During the diagnostic process, a patient’s medical team will review the medical history and perform a physical exam, which includes feeling for enlarged lymph nodes in the neck or arms.
ILC is often difficult to detect on a mammogram. If symptoms suggest ILC, other diagnostic tests such as an ultrasound or breast MRI may be performed to determine whether more tests are warranted. ILC can only be diagnosed by a biopsy, which is a procedure during which a sample of cells is removed from the breast and examined under a microscope, looking for the presence of cancer cells.
Each ILC is unique, but to better identify and treat each disease, ILC is grouped into stages. Breast cancer staging is performed using the TNM system (Tumor-Node-Metastasis). There are five stages.
Stage 0: This is also called in situ or noninvasive and refers to cancer that’s only found in the breast tissue ducts.
Stage 1: Cancer is small and invasive, but either hasn’t spread into the lymph nodes or has spread to the lymph nodes while remaining smaller than 2mm in the lymph nodes and less than 20mm in the breast.
Stage 2: The tumor is between 20mm and 50mm and may or may not have spread into the nearby lymph nodes.
Stage 3: The tumor is bigger than 50mm and has spread locally to other areas near the breast, such as the axillary or internal mammary lymph nodes or the lymph nodes near the collarbone.
Stage 4: Stage 4 is also known as metastatic cancer and is a cancer that’s spread to other areas of the body, which can include the brain, bones and lungs.
The treatment for ILC can vary, depending on the type of cancer, the patient’s preferences and preexisting health conditions.
ILC is also generally slow-growing cancer, which means patients have more time to make decisions on treatment. The most commonly used treatment options include:
Surgery: Surgery is a frequently used treatment for ILC. This could be a lumpectomy, which is the surgical removal of the breast tumor, along with a margin of healthy tissue from around the tumor; or a mastectomy, which is the complete removal of the breast. During or after the original surgery, breast reconstruction may be discussed as an elective option.
Radiation therapy: Radiation therapy is a treatment that uses high-energy X-rays to precisely target and kill cancer cells. The most common type is external beam radiation therapy, which uses a machine external to the body to deliver targeted radiation for a short period of time each day over several weeks.
Hormone therapy: For cancers that are hormone positive, hormone therapy can be used as a treatment option, sometimes given before or after surgery. Hormone therapy uses medication to lower hormone levels in the body, which makes it harder for cancer cells to grow.
Chemotherapy: Chemotherapy uses medication to kill cancer cells. There are a number of different chemotherapy drugs that are given over a course of several weeks.
Treatment options or any treatment side effects should be discussed with a patient’s medical team.