I was just diagnosed with a neurilemmoma of the arm. The tumor was removed but it turned out to be a nerve tumor in the bone. What causes that to happen?

Neurilemmomas (also known as schwannomas) occur in the nerve sheath (lining) of peripheral and cranial nerves. These nerves are located in the head (cranial nerves) and upper trunk and extremities (peripheral nerves).

Occasionally, these nerves are classified as intraosseous schwannomas. Intraosseous means within the bone. There are several possible means by which schwannomas can become intraosseous in nature.

The tumor cells may originate in the bone marrow where schwannoma cells are found. Or it could come from the nutrient vessel supplying blood to the bone. Sometimes, the tumor comes from the nerve tissue that erodes (eats) into the bone.

Bones affected most often include the jaw (because of the closeness to the cranial nerves of the head, face, and neck), the fibula (lower leg), and the sacrum. But these tumors can also affect the humerus (upper arm bone), radius, and the bones of the hands and feet.