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Neuroma originally was defined as a tumor of a nerve. (Neuro- is from the Greek for nerve). Today, neuroma commonly refers to any tumor of the nervous system. They can be either benign or malignant.
The most common type is a traumatic neuroma, which follows nerve injury (often as a result of surgery). They occur at the end of injured nerve fibres as a form of uneffective, unregulated nerve regeneration; it occurs most commonly near a scar, either superficially (skin, subcutaneous fat) or deep (e.g., after a cholecystectomy). They are often very painful.
Other neuromas can be categorised:
- Neurinoma (Neurilemmoma) - a benign slow growing tumor of the neurolemma (myelin sheath) of a nerve fiber.
- Neurofibroma (Schwannoma) - a benign tumor growing from the fibrous coverings of a peripheral nerve.
- Neuroblastoma - a malignant tumor arising from embryonic nerve cells in the sympathetic nervous system.
A special form of neuroma (named Morton's neuroma) occurs in the feet, near the distal metatarsal ends, by chronic pressure trauma to small nerve fibers related to gait; damaged nerve fibers are both fibrotic and hyperplastic.