Doctors performing an upper endoscopy for acid reflux, anaemia or indigestion can sometimes spot something called an incidental GIST, which stands for “gastrointestinal stromal tumour”.
It presents as a small bulge on the lining of the stomach or the intestine and is called “incidental” when discovered as part of a routine screening.
Fortunately, most GISTs are slow-growing, benign and small. If they’re caught at an early stage, they usually require minimal treatment.
Even so, they highlight the importance of getting regular endoscopies and check-ups. Patients who know that they have GISTs are in a better position than those who don’t.
What is a GIST exactly?
A GIST is a rare gastrointestinal tumour, comprising less than 1% of all GI cancers. Researchers believe it emerges from the dysfunction of interstitial cells of Cajal, which line the digestive tract. About two-thirds occur in the stomach, with the remaining third occurring in the small intestine or elsewhere.
It’s worth noting that GISTs do not grow from muscle layers, unlike polyps and adenocarcinomas. Because of this, they don’t usually cause symptoms until they get much larger.
Interestingly, the vast majority of patients never know that they have a GIST. Around 15 to 30% of them are completely asymptomatic.
Additionally, about 22.5% of people over the age of 50 have microscopic GISTs. Again, these are often asymptomatic.
What do GISTs look like on endoscopy?
GISTs are relatively straightforward to identify on endoscopies. Most are yellowish, firm, and smooth, or they can be the same colour as the lining of the GI tract while forming a submucosal bulge.
GISTs may look polyp-like; however, they can also be sessile. When they become larger, they can bleed and ulcerate.
Gastrointestinal specialists pay close attention to GISTs over 2 cm in diameter. These are most likely to cause symptoms. If they discover a growth, they will record it as a subepithelial lesion (SEL). This is a placeholder that tells the gastroenterologist to further investigate the case.
What happens after an incidental GIST diagnosis?
Your doctor will put you on a diagnostic pathway after discovering an incidental GIST. This starts with an endoscopic ultrasound. Here, doctors use a device that shows the precise location of the tumour in the wall of the GI tract. Usually, it’s in the muscularis propria, but it can be in other layers.
The next step is to check for the size and whether the tumor has any high-risk features. These can include:
- enlarged nodes
- irregular borders
- cystic spaces
After that, doctors will conduct a biopsy. This confirms whether the growth is truly a GIST via CD117 (c-kit) and DOG-1 proteins, which are present in more than 95% of cases
The final step is to confirm the risk level the GIST poses. Surgeons and gastroenterologists do this by measuring the location, cell turnover, weight, rate, and size. Fortunately, asymptomatic GISTs less than 2 cm in diameter with low division rates are usually low risk.
Treatment options for incidental GIST
Today, a watchful waiting approach is often recommended for incidental GISTs, particularly when they are small and not causing symptoms. This involves “active surveillance”, where the tumour is monitored over time for any changes in size or the development of high-risk features.
In many cases, follow-up endoscopy is performed at intervals of 12 to 24 months. Many of these tumours remain stable and carry a relatively low risk of becoming cancerous.
If treatment is required, it may involve one or more of the following:
- Endoscopic resection done under sedation, which removes the tumour completely while preserving the stomach lining
- Laparoscopic and robotic surgery using wedge resection
- Targeted therapy using drugs like imatinib for incidental small tumours where surgery isn’t immediately possible.
Patients who act early to remove GISTs often experience a full cure. They also benefit from excision techniques that preserve the entire stomach lining.
Why early detection matters
Early detection matters for incidental GISTs for several reasons:
- Removing them or managing them early prevents obstruction of the GI tract, bleeding (which can become a future emergency), or, in rare cases, metastasis.
- Small gastric GISTs carry a reasonable prognosis, and most patients require nothing more than active checks every one to two years.
If you are over 45 and have a family history of gastrointestinal conditions, it may be worth considering a gastroscopy, particularly if you have any concerning or unexplained symptoms. Early assessment can help detect previously unrecognised GISTs and guide appropriate monitoring or management over time.
If you have concerns about your digestive health or are unsure whether a gastroscopy is appropriate, consider seeking a consultation for further evaluation and personalised advice.