Overview

A schwannoma is a type of nerve tumor of the nerve sheath. It's the most common type of benign peripheral nerve tumor in adults. It can occur anywhere in your body, at any age.

A schwannoma typically comes from a single bundle (fascicle) within the main nerve and displaces the rest of the nerve. When a schwannoma grows larger, more fascicles are affected, making removal more difficult. In general, a schwannoma grows slowly.

If you develop a schwannoma in an arm or leg, you may notice a painless lump. Schwannomas are rarely cancerous, but they can lead to nerve damage and loss of muscle control. See your doctor if you have any unusual lumps or numbness.