Synonym
Schwannoma, Neurilemmoma, Benign Peripheral Nerve Sheath Tumor (BPNST) English : neurinoma
Introduction
The neurinoma is a slow-growing, benign tumor, which is usually surrounded by a capsule of connective tissue and grows displacement-not infiltrating the surrounding tissue. It is derived from so-called Schwann cells of the peripheral nervous system and develops at the cranial nerves and peripheral nerves.
Epidemiology
6-7% of all brain tumors are neurinomas, spinal neurinomas are the most common spinal tumors with 25%. Acoustic neuroma is the most common neurinoma, about 80% of all tumors in the cerebellar bridge angle are acoustic neuroma. About 10% of the patients with neurofibromatosis type 2 get a neurinoma, the frequency of neurofibromatosis type 2 is 1:50 000. The age of the disease is between 30 and 50 years, women are affected slightly more often than men.
Causes
The cause of a neurinoma is generally unknown. The most common known cause is neurofibromatosis type 2, very rarely also neurofibromatosis type 1. Neurofibromatosis type 2 is caused by a mutation of a gene on chromosome 22, a so-called NF-2 mutation, which is inherited dominantly.
Its frequency is 1:50 000. Neurofibromatosis type 1 (NF-1) is characterized by a defect on chromosome 17. It accounts for 90% of all neurofibromatoses and is also a dominant inherited disease with a frequency of 1:2000-3000. It is derived from the Schwann cells of the peripheral nervous system.
Appearance
A neurinoma is a tumor encapsulated in connective tissue with a bright, yellowish cut surface. The tumor cells are elongated and thin, their nuclei are pushed together in a row formation (palisade position). Microscopically, two types of tissue patterns can be distinguished:
- Antoni-A-Formation: fibrous and elongated cells with narrow, cigar-shaped nuclei that form trains, vortices and parallel nuclear rows.
- Antoni-B formation: low-fiber, net-like with often altered tissue changes such as fat deposits. The cell division activity is very low.