Invasive Lobular Carcinoma (ILC) represents a specific form of breast cancer that originates in the milk-producing glands of the breast. It is distinct from other types of breast cancer, as its unique cellular behavior influences how it presents, is identified, and subsequently managed.
Understanding Invasive Lobular Carcinoma
Invasive Lobular Carcinoma (ILC) is a type of breast cancer that develops in the lobules. Once the cancer cells break out of these lobules, they can spread into the surrounding breast tissue and potentially to other parts of the body through the blood and lymph systems. ILC is the second most common form of invasive breast cancer, accounting for approximately 5% to 15% of all invasive breast cancer diagnoses.
This type of cancer is characterized by a unique growth pattern where the cells tend to invade breast tissue by spreading out in single-file lines rather than forming a distinct, cohesive lump. This diffuse growth is largely due to the loss or dysfunction of E-cadherin, a protein responsible for cell-to-cell adhesion. In contrast, Invasive Ductal Carcinoma (IDC), the most common breast cancer type, typically forms a more defined mass.
The subtle infiltration of ILC cells makes it more challenging to detect through standard physical exams or imaging, often leading to a later diagnosis when tumors may be larger. ILC is frequently associated with and it commonly expresses estrogen and progesterone receptors. While generally considered slow-growing, its infiltrative nature can complicate accurate tumor size assessment.
Recognizing the Signs and How it’s Detected
Invasive Lobular Carcinoma often presents with subtle signs, making early detection challenging. Unlike the distinct lump commonly associated with other breast cancers, ILC may manifest as an area of thickening, swelling, or fullness in the breast. Other potential indications include a newly inverted nipple, subtle changes in breast size or shape, or a different texture of the breast skin, such as dimpling. These less obvious symptoms can be attributed to the cancer cells spreading diffusely rather than forming a solid mass.
Given its diffuse growth pattern, ILC can be difficult to detect on conventional mammography. Mammograms may show subtle features like architectural distortion or asymmetric density, but microcalcifications are uncommon. Digital breast tomosynthesis (DBT) can improve detection compared to standard mammography, though findings can still be subtle.
Ultrasound is another diagnostic tool, often revealing a hypoechoic mass with irregular or indistinct margins and posterior acoustic shadowing. Breast Magnetic Resonance Imaging (MRI) is frequently more effective for ILC detection, particularly for identifying additional cancer foci and assessing the full extent of the disease. A definitive diagnosis of ILC always requires a breast biopsy, where tissue samples are examined under a microscope to confirm the presence of cancer cells and determine their characteristics.
Approaches to Treating ILC
Treatment for Invasive Lobular Carcinoma typically begins with surgery to remove the cancerous tissue. Surgical options include lumpectomy, which removes the tumor and a margin of healthy tissue, or mastectomy, involving the removal of all breast tissue. Sentinel lymph node biopsy is commonly performed during surgery to check for cancer spread to nearby lymph nodes.
Following surgery, radiation therapy is often recommended, especially after a lumpectomy, to eliminate any remaining cancer cells in the breast and reduce the risk of local recurrence. Radiation therapy typically involves external beam radiation, where a machine directs energy to precise points on the body.
Systemic therapies are also a standard part of ILC treatment. Hormone therapy is a common approach because most ILCs are hormone receptor-positive. Medications, such as aromatase inhibitors, work by blocking hormones from attaching to cancer cells or by reducing hormone production, often prescribed for at least five years after surgery.
Chemotherapy may be used, though ILC is generally considered less responsive to it compared to other breast cancer types due to its biological characteristics. However, chemotherapy can be beneficial in certain situations, such as shrinking a large tumor before surgery (neoadjuvant therapy) or for patients with a high risk of recurrence. Targeted therapies are also considered. Most ILCs do not overexpress HER2, so HER2-targeted therapies are less commonly used unless the cancer tests positive for this protein.
Navigating Life After Treatment
After completing primary treatment for Invasive Lobular Carcinoma, ongoing care and surveillance are important for monitoring health and detecting any potential recurrence. Regular follow-up appointments, including physical examinations, are recommended one to four times per year for five years, then annually. These visits allow healthcare providers to assess for signs of recurrence, both in the treated breast area and in distant parts of the body.
Annual mammography is a standard part of surveillance for patients who underwent breast-conserving surgery. However, due to ILC’s diffuse growth, mammography may not detect all local recurrences, and supplemental imaging like breast MRI may be considered, especially for those with a higher risk of a second primary breast cancer. Adherence to prescribed hormone therapy is also emphasized, as it helps reduce the risk of cancer returning.