Invasive Lobular Carcinoma Overview

Invasive lobular carcinoma (ILC) is a common type of breast cancer that originates in the milk-producing glands (lobules) and spreads to the surrounding breast tissues. If left untreated, the tumor can also invade nearby lymph nodes and metastasize to other areas of the body.

ILC accounts for up to 15% of all invasive breast cancers, making it the second most frequently diagnosed type after invasive ductal carcinoma (IDC), which originates in the thin tubes (ducts) that carry milk from the lobules to the nipple.

What causes invasive lobular carcinoma?

ILC begins with abnormal changes in the cells of the lobules. These harmful genetic mutations can promote uncontrolled cell growth, disrupt the normal function of tumor-suppressing genes and activate oncogenes, all of which can lead to tumor formation. While the precise cause of invasive lobular carcinoma is unclear, scientists believe it likely occurs due to a combination of spontaneous cellular changes and underlying biological processes that drive the development, progression and invasiveness of breast cancer.

What are the risk factors for invasive lobular carcinoma?

Known risk factors for ILC include:

• Advanced age – Breast cancer risk generally increases with age, with invasive lobular carcinoma most frequently diagnosed in women 55 and older.
• Hormone replacement therapy (HRT) – Prolonged use of postmenopausal HRT, particularly estrogen and progesterone, has been linked to an increased risk of ILC.
• Family history – A family history of breast cancer increases the likelihood of developing invasive lobular carcinoma.
• Breast cancer gene mutations – A mutation in breast cancer gene 1 (BRCA1) or breast cancer gene 2 (BRCA2) can elevate the risk of developing many types of breast cancer, including ILC.
• Dense breast tissue – Women with dense breast tissue may have a higher risk of developing invasive lobular carcinoma.
• Prior radiation therapy – A history of radiation therapy to the chest, especially at a young age, increases the risk of breast cancer.
• Alcohol consumption – Excessive drinking can increase the risk of many types of cancer, including ILC.
• Obesity – Postmenopausal women with obesity are at heightened risk for breast cancer due to the increased levels of estrogen produced by fatty tissue (adipose).
• Reproductive history – Women who have never been pregnant or had their first pregnancy late in life may be at higher risk for invasive lobular carcinoma.

What are the symptoms of invasive lobular carcinoma?

The symptoms of ILC are often subtle, making early detection a challenge. While other types of breast cancer cells typically form clumps or masses that can be felt or seen in images, ILC cells usually grow into lines, which can be difficult to detect during a physical examination or see on a mammogram.

Possible warning signs of invasive lobular carcinoma include:

• Breast thickening or hardening – Rather than creating a distinct breast lump, ILC may produce an area of thickened or hardened tissue that can be felt.
• Breast asymmetry – One breast may appear larger, smaller, fuller or differently shaped than the other breast.
• Breast swelling – Unexplained fullness may develop in one area of the breast.
• Breast skin changes – Dimpling, puckering or other changes may occur in the texture of the breast skin.
• Newly inverted nipple – The nipple may turn inward or lie flat against the breast instead of pointing outward.
• Breast pain – While less common than other ILC symptoms, localized breast pain or tenderness may occur in some cases.
• Thickening in the armpit – Unusual swelling or a lump that can be felt in the underarm area may indicate lymph node involvement.

How is invasive lobular carcinoma diagnosed?

The diagnostic process for ILC typically begins with a clinical assessment. A physician will assess the breasts for abnormalities, such as thickened areas and changes in shape or skin texture. To follow up on any unusual findings, the physician will likely order imaging tests, such as:

• Mammography – Although mammography is often the first imaging test used to diagnose breast cancer, its usefulness in diagnosing ILC is limited because the cancer typically does not form a distinct lump that can be seen on an X-ray.
• Ultrasound – By using a transducer to direct high-frequency sound waves through the skin, a specially trained medical professional (sonographer) can create detailed images of the breast tissues to help the physician evaluate areas of concern.
• Magnetic resonance imaging (MRI) – Often used to further evaluate breast abnormalities, particularly in cases where ILC is suspected, MRI is a highly sensitive imaging modality that can reveal subtle and diffuse changes in breast tissues, including the non-mass-like patterns characteristic of invasive lobular carcinoma.

Like all types of breast cancer, a definitive diagnosis of ILC requires a biopsy. Common biopsy techniques include:

• Fine needle aspiration (FNA) – FNA involves the use of a thin needle to extract cells or fluid from the suspicious area.
• Core needle biopsy – The most commonly used type of biopsy for invasive lobular carcinoma, a core needle biopsy involves the use of a hollow needle to remove small tissue samples from the affected area of the breast.
• Stereotactic biopsy – A specialized type of core needle biopsy, stereotactic biopsy involves the use of mammography to help the physician precisely locate and sample abnormal areas of the breast.
• Excisional biopsy – Also known as a wide local excision, this surgical procedure involves the removal of the entire lesion along with a slim margin of surrounding tissue.

The tissue samples will be sent to a laboratory for microscopic examination by a pathologist, who can detect cancerous cells. ILC can be identified by its distinctive pattern of cancer cells, which are usually spread in single-file lines, and the loss of E-cadherin protein, which normally helps the cells adhere to each other.

After confirming a diagnosis of invasive lobular carcinoma, the physician may order testing for hormone receptors (estrogen and progesterone) and HER2 status. The results can be used to guide treatment decisions.

How is invasive lobular carcinoma treated?

ILC treatment usually involves a multimodal approach tailored to the stage and hormone-receptor status of the tumor and the overall health and preferences of the patient. Options may include:

• Observation – In a low-risk case, a wait-and-watch approach may be considered.
• Lumpectomy – A surgeon will remove the tumor and a slim margin of surrounding healthy tissue, preserving most of the breast tissue.
• Mastectomy – A surgeon will remove all breast tissue, including the nipple, areola and skin.
• Radiation therapy – Often used after a lumpectomy, radiation therapy can target any remaining microscopic cancer cells and help reduce the risk of recurrence.
• Hormone therapy – For hormone-receptor-positive ILC, medications such as tamoxifen or aromatase inhibitors may be used to block the cancer-growth-stimulating effects of estrogen and progesterone.
• Targeted therapy – For HER2-positive ILC, medications such as trastuzumab (Herceptin) may be used to specifically target HER2 proteins.
• Chemotherapy – Chemo may be considered for aggressive or metastatic ILC.

Benefit from world-class care at Moffitt Cancer Center

The multispecialty team in Moffitt’s nationally recognized Don & Erika Wallace Comprehensive Breast Program takes a collaborative, patient-focused approach to breast cancer care. Our patients can benefit from the latest diagnostic, treatment and supportive care options for invasive lobular carcinoma, including promising new therapies available only through our robust clinical trials program.

If you would like to learn more about invasive lobular carcinoma, you can request an appointment with a breast cancer specialist at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.