A schwannoma is a benign, or non-cancerous, tumor. It develops on the sheath or cover of a nerve and grows from there. They are not necessarily painful but can cause pain if they begin to press on the nerves. They are usually very slow growing. Usually schwannomas don’t interfere with the nerves unless they are on a major nerve.
Tests to diagnose schwannomas can include x-rays to be sure the mass isn’t interfering with a bone, ultrasounds to allow the doctor to see the organs around it, magnetic resonance imaging (MRI) to give more detailed images, and a biopsy of the tumor. To do a biopsy, the doctor takes a small piece of tissue from the tumor and it is examined under a microscope to check for cancerous cells.