A lipoma is a benign tumor composed of adipose tissue (body fat). It is the most common benign form of soft tissue tumor.Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small (under one centimeter diameter) but can enlarge to sizes greater than six centimeters.Lipomas are commonly found in adults from 40 to 60 years of age, but can also be found in younger adults and children.ipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small (under one centimeter diameter) but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults from 40 to 60 years of age, but can also be found in younger adults and children.