Invasive Lobular Carcinoma - Early Signs, Risk Factors, Diagnosis, and Treatment Explained

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer, after invasive ductal carcinoma. It begins in the milk-producing glands of the breast, called lobules, and then spreads to surrounding breast tissue. Over time, it can also spread (metastasize) to other parts of the body through the lymph nodes or bloodstream.

ILC accounts for about 10–15% of invasive breast cancers. While it is less common than ductal carcinoma, it has unique features that make it harder to detect in the early stages. A hallmark biological feature is loss of the cell adhesion protein E-cadherin (CDH1), which makes tumor cells grow in single-file strands. This pattern often makes invasive lobular carcinoma more difficult to detect on exam or mammogram compared with ductal cancers. Unlike other breast cancers, invasive lobular carcinoma often does not form a distinct lump. Instead, it may cause subtle thickening or fullness in the breast, which can be missed during breast self-exams or even on mammograms.

Early detection matters because breast cancer, including ILC, has a much better chance of successful treatment and long-term survival when diagnosed before it spreads.

What Are the Types of Invasive Lobular Carcinoma?

There are a few subtypes of invasive lobular carcinoma. Each behaves slightly differently and may affect treatment choices:

• Classic ILC: The most common type. Cancer cells grow in a single-file pattern and often spread widely within the breast tissue.
• Alveolar type: Cancer cells form small groups within the breast tissue.
• Solid type: Cells grow in tight clusters, resembling solid masses.
• Pleomorphic type: A more aggressive subtype, with cells that look abnormal under the microscope.
• Tubulolobular type: A mix of tubular carcinoma and lobular carcinoma features.

Understanding the subtype helps doctors create a treatment plan tailored to each patient.

What Are the Causes of Invasive Lobular Carcinoma?

Like most cancers, invasive lobular carcinoma does not have a single cause. Instead, it develops from changes (mutations) in the DNA of breast cells. These changes cause cells to grow uncontrollably and spread. Some DNA changes may be inherited, while others develop over a person’s lifetime due to aging, hormonal influences, or environmental exposures.

What Are the Risk Factors for Invasive Lobular Carcinoma?

Certain factors can increase the chance of developing invasive lobular carcinoma:

• Age: Most cases occur in women over age 55
• Gender: Women are at much higher risk, but men can also develop ILC
• Family history of breast cancer: Having close relatives with breast or ovarian cancer increases risk
• Inherited genetic mutations: BRCA1, BRCA2, and CDH1 mutations are linked to lobular cancer
• Hormone replacement therapy (HRT): Long-term use of combined estrogen-progestin therapy after menopause raises risk
• Reproductive history: Early menstruation, late menopause, or never having children may increase risk
• Lifestyle factors: Obesity, alcohol use, and lack of physical activity can contribute
• Previous radiation therapy to the chest: Raises risk years later

Having one or more risk factors does not mean someone will definitely get invasive lobular carcinoma, but it does increase the likelihood.

What Are the Symptoms of Invasive Lobular Carcinoma?

Invasive lobular carcinoma can be harder to detect than other breast cancers because it usually does not form a firm lump. Symptoms may include:

• A thickened or hard area in the breast
• A feeling of fullness or swelling in part of the breast
• A change in breast size or shape
• Dimpling or pulling in of the skin
• Nipple changes, such as inversion (turning inward)
• Pain or discomfort in the breast (less common)
• In advanced cases, symptoms may include swelling in the underarm, unexplained weight loss, or bone pain if the cancer has spread.

Because invasive lobular carcinoma spreads in thin strands, mammograms can miss it. MRI is often more sensitive when suspicion remains high.

How Is Invasive Lobular Carcinoma Diagnosed?

Doctors use a combination of physical exams, imaging, and biopsy to confirm invasive lobular carcinoma.

• Clinical breast exam: A doctor performs a breast exam to check for thickening or changes
• Mammogram: X-ray images of the breast may catch signs of invasive lobular carcinoma, however, it may also miss ILC because it doesn’t always form a lump
• Breast ultrasound: Helps detect suspicious changes to the breast tissue
• MRI scan: This is often more effective in identifying invasive lobular carcinoma
• Core needle biopsy: A tissue sample is taken and examined under a microscope to confirm the presence of cancer and the type.
• Hormone receptor and HER2 testing: These tests determine if the cancer is sensitive to estrogen, progesterone, or HER2, which guides more accurate treatment.
• Ki-67 Proliferation Index: An immunohistochemistry test that measures the percentage of tumor cells that are actively dividing, using an antibody to detect the Ki-67 protein. A higher index indicates faster cell growth and can predict a more aggressive cancer

Staging of Invasive Lobular Carcinoma

Staging describes how far cancer has spread:

• Stage I: Small, localized tumor
• Stage II: Larger tumor or spread to nearby lymph nodes
• Stage III: More extensive spread to lymph nodes or nearby tissues
• Stage IV: Cancer has spread to distant organs (metastatic breast cancer)

Grading describes how abnormal the cancer cells look under the microscope. Low-grade tumors grow slowly, while high-grade tumors grow more aggressively. Staging and grading help doctors decide the most effective treatment plan.

What Are the Treatment Options for Invasive Lobular Carcinoma?

Treatment depends on stage, grade, hormone receptor status, and overall health. Common approaches include:

Surgery

• Lumpectomy (breast-conserving surgery): Removal of only the tumor and some surrounding tissue, preserving most of the breast.
• Mastectomy: Removal of the entire breast. Types of mastectomies include simple mastectomy, modified radical mastectomy, skin- and nipple-sparing mastectomy, endoscopy-assisted mastectomy, and prophylactic mastectomy.
• Sentinel lymph node biopsy: Checks whether cancer has spread to the lymph nodes near the breast. Sentinel lymph node biopsy is standard for axillary staging. If one or two sentinel nodes are positive, many women can avoid full axillary dissection and instead receive radiation, depending on tumor characteristics.

Medical Treatments

• Hormone therapy: Hormone therapy is the backbone of invasive lobular carcinoma treatment. Medicines like tamoxifen or aromatase inhibitors block hormones like estrogen and progesterone that fuel certain cancers. In high-risk premenopausal women, ovarian function suppression may be added.
• Targeted therapy: Uses mutations in cancer cells as its target, employing precision medicine to selectively attack cancer cells while minimizing damage to healthy cells. In invasive lobular carcinoma, common mutations include PIK3CA mutation, ESR1 mutation and HER2-low.
• Chemotherapy: Uses strong medicines to kill cancer cells.

Radiation Therapy

High-energy X-ray beams destroy remaining cancer cells after surgery, especially after a lumpectomy.

Proton Therapy: When Is It Applicable?

Available at Apollo Proton Cancer Centre, proton therapy uses protons instead of X-rays to deliver radiation more precisely to cancer cells. This allows doctors to target the tumor while minimizing damage to healthy surrounding tissue, including the heart and lungs.

Proton therapy may be considered for invasive lobular carcinoma in the following situations:

• When the tumor is located close to critical organs such as the heart or lungs, especially in left-sided breast cancers.
• In younger patients, to reduce long-term side effects from radiation exposure.
• For patients who have already received radiation to the chest and require additional treatment.
• In complex cases where precision is essential to reduce radiation-related complications.

While proton therapy is not required for all patients with invasive lobular carcinoma, it can be especially beneficial in selected cases where traditional radiation may pose higher risks.

What is the Prognosis for Invasive Lobular Carcinoma?

The outlook for invasive lobular carcinoma depends on the stage at diagnosis, hormone receptor status, and overall health.

• Early-stage invasive lobular carcinoma has a very good survival rate, often above 90% at 5 years.
• Advanced-stage invasive lobular carcinoma has a lower survival rate but can often be managed for many years with treatment.
• Hormone receptor-positive cancers usually respond well to hormone-blocking therapies, improving long-term outcomes.

Screening and Prevention of Invasive Lobular Carcinoma

• Mammograms: Women aged 40 and older should get regular mammograms, which can spot early signs of cancer, even before it can be felt.
• Breast Self-exams: Regular breast self-examinations can help detect changes in the breast.
• Lifestyle changes: Maintain a healthy optimal weight, exercise regularly, avoid alcohol and smoking.
• Genetic testing: High-risk women, including those with a strong family history of cancer, may consider BRCA or CDH1 testing.

For International Patients

People from around the world come to Apollo Hospitals for the treatment of invasive lobular carcinoma. Our international patient services team will guide you all the way from seeking the first virtual connect all the way to treatment in India and then returning home post treatment.

Services include:

• Medical opinions and scheduling
  • Pre-arrival medical review of reports and imaging.
• Travel and logistics
  • Assistance with visa invitation letters, airport transfers, and nearby accommodation options.
  • Dedicated international patient coordinators to guide through each step.
• Language and cultural support
  • Interpreter services in multiple languages.
  • Clear, simple explanations at every stage with written care plans.
• Financial coordination
  • Transparent treatment estimates and packages when possible.
  • Support with international payment methods and insurance coordination.
• Continuity of care
  • Shared records, imaging, and treatment summaries for home doctors.
  • Telemedicine follow-ups for convenience after returning home.

Frequently Asked Questions (FAQs)

1. What is the survival rate of invasive lobular carcinoma?

 A: The 5-year survival rate is over 90% when detected early, but it decreases in advanced stages.

2. Can invasive lobular carcinoma come back after treatment?

 A: Yes, recurrence is possible. Regular follow-ups and screenings are important to monitor long-term health.

3. What are the side effects of invasive lobular carcinoma treatment? 

A: Side effects vary by treatment: fatigue, nausea, hair loss, hot flashes, and joint pain are common but manageable with medical support.

4. How long is recovery after breast cancer surgery? 

A: Most women recover from lumpectomy in 2–4 weeks and mastectomy in 4–6 weeks. Recovery also depends on additional treatments like chemotherapy or radiation.

5. Can invasive lobular carcinoma be cured? 

A: When detected early and treated effectively, many patients are cured. In advanced cases, treatment focuses on control and quality of life.

6. Is proton therapy better for invasive lobular carcinoma? 

A: Proton therapy can be beneficial in specific cases where traditional radiation may harm nearby organs, but it is not necessary for every patient.