|· Benign, usually encapsulated tumor composed of differentiated neoplastic Schwann cells.· WHO grade I
· Most common peripheral nerve tumor, generally occurring in the head and neck region and in the extremities, more frequently along the surfaces. Only on occasion is the parent nerve identified.
· Most conventional are solitary, sporadic tumors.
· Rarely associated with radiation.
· May arise intracranially, and intraspinally, affecting sensory nerves, such as the vestibular nerve and dorsal spinal nerves.
· Intraspinally in the cervicothoracic area frequently involve the intervertebral foramen and show an intra and an extradural “dumbbell” configuration.
· Macroscopic feature—typically globular or ovoid, well circumscribed with a smooth surface. Peripheral tumors are usually surrounded by well formed capsule, often thick and fibrocartilagenous. A parent nerve is identifiable in less than half of cases, most often when the tumor arises in a sizable nerve.
· Microscopic feature—consist entirely of neoplastic Schwann cells, grow in solid, noninfiltrative fashion and lie eccentric to their parent nerve. Nerve fibers therefore are not dispersed within the substance of the tumor, but, when identifiable, lie in bundles adjacent to or within its capsule.