These are benign, slow-growing nerve tumors, similar to schwannomas. They commonly occur in patients who suffer from neurofibromatosis, a genetic disorder resulting in multiple tumors throughout the body.They can occasionally occur in patients without this genetic abnormality.
Cutaneous neurofibromas grow along small branches of nerves under the skin of patients with neurofibromatosis. They may present as painful lumps under the skin. They are not associated with large nerves, and are easily removed.
Figure 1. Intraoperative, magnified view of a cutaneous neurofibroma with associated small cutaneous sensory nerve just prior to excision.
Larger neurofibromas tend to grow within large, important nerves. Unlike schwannomas, however, they are more intimately intertwined with the nerve fibers, making removal more difficult. Nevertheless, with meticulous surgical technique, these difficult tumors may be safely removed, causing few if any deficits.
Figure 2. Intraoperative view of a medium-sized median nerve neurofibroma.
Figure 3. Intraoperative view of the same patient seen in Figure 2, following removal of the tumor. The nerve is both anatomically and functionally intact. The patient awakened without any deficit.
When a neurofibroma involves a particularly long segment of nerve or nerves, it is called a plexiform neurofibroma. These are generally impossible to remove without removing the entire nerve, necessarily causing a major neurological deficit. Therefore, these variants are not usually subjected to surgery.
A small percentage of plexiform neurofibromas change from benign to malignant, and can spread to other parts of the body. These cancers are almost uniformly lethal without aggressive treatment. If a plexiform neurofibroma becomes exceptionally painful and/or begins to rapidly expand, this suggests it has become cancerous, and it must be definitively treated.
Figure 4. Intraoperative view of a plexiform neurofibroma that had become painful. A biopsy was performed that showed that tumor was not malignant. Not that the tumor diffusely involves the nerve, and does not form a discreet mass that is amenable to excision. Removing this tumor would require removing the entire segment of nerve, an unacceptable option as this would produce severe neurological deficits.