Invasive lobular carcinoma (ILC), sometimes called infiltrating lobular carcinoma, is the second most common type of breast cancer after invasive ductal carcinoma (cancer that begins in the milk-carrying ducts and spreads beyond it). According to the American Cancer Society, more than 180,000 women in the United States find out they have invasive breast cancer each year. About 10% of all invasive breast cancers are invasive lobular carcinomas. (About 80% are invasive ductal carcinomas.)
Invasive means that the cancer has “invaded” or spread to the surrounding breast tissues. Lobular means that the cancer began in the milk-producing lobules, which empty out into the ducts that carry milk to the nipple. Carcinoma refers to any cancer that begins in the skin or other tissues that cover internal organs — such as breast tissue. All together, “invasive lobular carcinoma” refers to cancer that has broken through the wall of the lobule and begun to invade the tissues of the breast. Over time, invasive lobular carcinoma can spread to the lymph nodes and possibly to other areas of the body.
Although invasive lobular carcinoma can affect women at any age, it is more common as women grow older. According to the American Cancer Society, about two-thirds of women are 55 or older when they are diagnosed with an invasive breast cancer. ILC tends to occur later in life than invasive ductal carcinoma — the early 60s as opposed to the mid- to late 50s.
Some research has suggested that the use of hormone replacement therapy during and after menopause can increase the risk of ILC.