A lipoma is a benign tumor made of fat cells that appears as a soft lump beneath the skin. It usually forms on the upper back and thighs, shoulders, arms, and buttocks. Occasionally, it may be located deeper beneath the skin in the thighs, shoulders, or calves.
In most patients, lipomas are painless. They don’t usually change after they form and generally won’t become cancerous. They can, however, continue to grow over time, which may cause pain if they begin to press against a nerve.
You can be diagnosed with one of several forms of lipoma, including a conventional lipoma, hibernoma, fibrolipoma, angliolipoma, myelolipoma, spindle cell lipoma, pleomorphic lipoma, or an atypical lipoma.