Causes

It's not clear what causes invasive lobular carcinoma.

Doctors know that invasive lobular carcinoma begins when cells in one or more milk-producing glands of the breast develop mutations in their DNA. The mutations lead to the inability to control cell growth, which results in the cells dividing and growing rapidly. Depending on the aggressiveness of the cancer type, the cancer cells can spread to other parts of the body.

Lobular carcinoma cells tend to invade breast tissue by spreading out in a distinct way rather than forming a firm nodule. The affected area may have a different feel from the surrounding breast tissue, more like a thickening and fullness, but it's unlikely to feel like a lump.