Gastrointestinal Neurofibromas

What gastrointestinal neurofibromas are

Neurofibromas grow from the cells that wrap nerves (Schwann cells) along with other supporting cells. In neurofibromatosis type 1, a genetic change in the NF1 gene, which normally acts as a brake on cell growth, allows these tumors to form throughout the body: in the skin, along deeper nerves and, less often, in internal organs.

In the digestive tract, neurofibromas can be:

• single or multiple nodules in the stomach or intestinal wall
• plexiform neurofibromas that spread along the nerve networks of the bowel or mesentery
• diffuse ganglioneuromatosis, a thickening of the bowel wall by nerve tissue

The small intestine (especially the jejunum) is most often involved, followed by the stomach and colon.

How common they are

Gastrointestinal involvement of some kind is found in a minority of people with NF1, though many small tumors never cause symptoms and are discovered by chance. Isolated GI neurofibromas without NF1 are rare.

Related gastrointestinal tumors in NF1

People with NF1 are more likely to develop:

Symptoms

• Bleeding: slow bleeding causes iron-deficiency anemia, tiredness and pale skin; faster bleeding causes black stools or blood in the stool
• Abdominal pain and bloating
• Constipation or altered bowel habits, especially with ganglioneuromatosis
• Bowel obstruction: vomiting, cramping pain, swollen belly
• Intussusception: a tumor acts as a lead point, pulling one part of the bowel into another
• A palpable mass in the belly
• Jaundice if a tumor near the duodenum blocks the bile duct

Diagnosis

• Blood tests: blood count and iron studies for anemia
• Stool tests for hidden blood
• CT or MRI of the abdomen to locate tumors and look for blockage
• Upper endoscopy and colonoscopy
• Capsule endoscopy or balloon enteroscopy to see the small intestine, where many tumors are hidden
• Biopsy to distinguish neurofibroma from GIST or other tumors
• PET-CT if malignant change is suspected in a plexiform neurofibroma

Treatment

• No symptoms: monitoring by an NF1 specialist team
• Surgery: removal of the affected segment of bowel for bleeding, blockage, intussusception or a tumor that is growing or suspicious
• Endoscopic treatment for some small bleeding lesions
• Iron replacement or transfusion for anemia
• MEK inhibitors (such as selumetinib) for symptomatic, inoperable plexiform neurofibromas in children, and increasingly in adults
• GIST treatment: surgery; NF1-associated GISTs often respond poorly to imatinib, unlike typical GISTs

Living with NF1

People with NF1 benefit from care in a multidisciplinary NF clinic, with regular checks of skin, eyes, blood pressure, development and any new symptoms. Report persistent or unusual digestive symptoms, unexplained anemia, or a neurofibroma that becomes painful or grows quickly. Genetic counseling explains the 50 percent chance of passing NF1 to each child.

Frequently asked questions

What are gastrointestinal neurofibromas?

They are benign tumors of nerve sheath cells in the wall of the stomach or intestines, usually in people with neurofibromatosis type 1. Many cause no symptoms, but some cause bleeding, pain, anemia or bowel blockage.

Can NF1 affect the digestive system?

Yes. NF1 can cause neurofibromas in the gut wall, diffuse nerve tissue thickening, and raises the risk of GIST and duodenal neuroendocrine tumors. Symptoms include bleeding, anemia, pain, constipation and obstruction.

Are gastrointestinal neurofibromas cancerous?

Neurofibromas are benign, but plexiform neurofibromas have a small lifetime risk of turning into a malignant peripheral nerve sheath tumor. Rapid growth, new pain or hardness should be checked promptly. People with NF1 also have a higher risk of GIST.

How are gastrointestinal neurofibromas treated?

Tumors without symptoms are usually monitored. Surgery is used for bleeding, blockage, intussusception or suspicious growth. MEK inhibitor medicines can shrink some inoperable plexiform neurofibromas. Anemia is treated with iron.