What is invasive lobular carcinoma?
Invasive breast cancers are those that have broken out of the areas where they originated and infiltrated surrounding breast tissue. The most common type of invasive breast cancer is invasive ductal carcinoma, followed by invasive lobular carcinoma.
Ninety-five percent of invasive lobular carcinoma tumors are estrogen receptor (ER)–positive and 70 percent are progesterone receptor (PR)–positive. Sixty to 70 percent are both ER- and PR-positive. Lobular carcinoma typically expresses low or no HER2 protein (referred to as HER2-negative). These characteristics make lobular breast cancer a suitable candidate for endocrine therapies. However, invasive lobular carcinomas often become resistant to therapy.
The lobular form of breast cancer occurs more frequently in postmenopausal women and tends to be diagnosed at later, more advanced stages (more on that below). Lobular carcinoma is rare in men, representing less than two percent of all male breast cancers.
Lobular breast cancer has distinct biological characteristics that set it apart from ductal carcinoma. A hallmark feature of classical invasive lobular breast cancers is that the tumors grow in single-file strands rather than the more common “lump” seen in invasive ductal breast cancers. Other lobular breast cancer variants are characterized by distinct cell configurations, such as solid, honeycomb-like assemblies (alveolar), tube-like strands (tubule-lobular), and mixes of variants. These variants all have diffused growth patterns that just slightly disturb the normal tissue architecture, making them harder to detect by physical exam or mammography.
The unique tumor growth patterns of lobular breast cancer are caused by a genetic alteration in the CDH1 gene that codes for E-cadherin, a protein that is essential for cell-to-cell adhesion that promotes normal tissue structure. A loss of CDH1 is the most prevalent gene alteration that distinguishes invasive lobular from invasive ductal cancer. Loss of E-cadherin function is associated with increased tumor development, invasiveness, and metastasis (spreading to distant sites in the body).
Symptoms
In many cases, invasive lobular carcinoma causes no symptoms and is found after your doctor sees a suspicious area on a screening mammogram.
In other cases, you or your doctor may feel a thick or swollen area in your breast. ILC is less likely than other breast cancers to cause a hard lump. Any of the following unusual changes in the breast can be a first sign of invasive lobular carcinoma:
swelling of all or part of the breast
skin irritation
Skin dimpling, sometimes looking like an orange peel.
breast or nipple pain
nipple discharge, other than breast milk
Redness, scaliness, or thickening of the nipple or breast skin.
A lump or swelling in the underarm area.
An area of thickening in part of the breast
A new area of fullness or swelling in the breast.
A change in the texture or appearance of the skin over the breast, such as dimpling or thickening.
A newly inverted nipple
Invasive lobular carcinoma is less likely than other forms of breast cancer to cause a firm or distinct breast lump.
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