Gastrointestinal Stromal Tumors (GIST) in young people is known as pediatric GIST. It is thought to be very rare. There are important differences between pediatric GIST and adult GIST. Pediatric GIST can be further divided into subgroups. The most familiar and perhaps the most common type is simply called “Pediatric GIST.” It most commonly affects girls between the ages of about 6 to 18 and almost always starts in the stomach. It can occur after the age of 18 however.

The second well-known type of GIST affecting young people is called “Carney’s Triad.” It is named after Dr. J. Aidan Carney who first described it in 1977. Patients with Carney’s triad may have several different types of tumors including GIST, pulmonary chondroma, and/or functioning extra-adrenal paraganglioma. If any two of these tumors are present, a diagnosis of the "triad" can be made, particularly if age and sex factors are supportive.

Two additional subtypes of pediatric GIST are even more rare: Carney-Stratakis Syndrome, (Familial Paraganglioma and Gastric Stromal Sarcoma) is a rare type of pediatric GIST that runs in families, and "Neonatal GIST" occurs in newborns.

Emerging evidence suggests that the various forms of Pediatric GIST are related by deficiencies of a protein called succinate dehydrogenase. Patients that have Carney-Stratakis Syndrome have mutations in one of the sub-units that make up this protein and patients with Pediatric GIST or Carney's Triad have lost the function of this protein through some unknown means.