The causes of lipomas, also called benign fatty tumors, vary based on the age and health condition of each patient. They are not cancerous, but they can cause discomfort and other symptoms if they grow large enough to compress nerves or interrupt other body functions. Learn about the most common causes of these tumors.hile most lipomas are found under the skin, they may be found in muscles and near organs inside the body such as the brain, the heart, or the spine. Lipomas can be diagnosed by your doctor feeling the fatty tumor.