Infiltrating (Invasive) Lobular Carcinoma (ILC)

Infiltrating lobular carcinoma accounts for about 5 percent of all malignant, invasive cancers. It occurs most frequently in women between the ages of 45 and 56. The tumor grows in the terminal (last part) of the lobules where milk is produced. It usually does not show up on mammography and may feel like a thickening in the upper-outer quarter of the breast (from the nipple to under the arm) as it infiltrates the walls of the lobules. In about 30% of cases, this cancer is frequently found in the opposite breast. It is often found in other parts of the same breast (multicentric). Late signs of a large tumor area may be the retraction or puckering of the skin over the area. Most tumors are positive for estrogen and progesterone receptors and thus respond well to hormonal therapy. Infiltrating lobular carcinoma sometimes has an increased incidence of spreading to the uterus and ovaries.