GISTs are the commonest mesenchymal tumours of the GI tract, arising from the interstitial cells of Cajal. They are found most often in the stomach and small bowel. Most carry an activating KIT or PDGFRA mutation, which determines targeted therapy. The cornerstone is complete surgical resection (R0); imatinib is used as adjuvant or neoadjuvant treatment in high-risk tumours.
What are GISTs?
GISTs (Gastrointestinal Stromal Tumors) are the commonest mesenchymal tumours of the GI tract. They arise from the interstitial cells of Cajal — the "pacemaker" cells that regulate gut motility — or their precursors. They differ from carcinomas, which are epithelial in origin, and from other sarcomas.
They are not simply "benign" or "malignant": they show a spectrum of malignant potential, assessed from the tumour's size, mitotic count and location.
How common are they?
Although rare compared with adenocarcinomas, GISTs are the commonest mesenchymal tumours of the GI tract. They are found most often in the stomach (around two thirds of cases), followed by the small bowel, and less often the colon and rectum, oesophagus or extra-intestinal sites.
A significant proportion are discovered incidentally, on endoscopy or a CT scan performed for another reason.
How do they present?
Many GISTs are asymptomatic. When they do cause symptoms, these depend on size and site:
- GI bleeding — the commonest finding, from ulceration of the overlying mucosa, which may present as melaena or anaemia.
- Vague abdominal pain or discomfort, a feeling of fullness and early satiety.
- A palpable mass with larger tumours.
- More rarely, an acute abdomen if the tumour ruptures.
How is it diagnosed?
Work-up combines endoscopy, imaging and histological/molecular confirmation:
- Endoscopy — reveals a submucosal lesion with intact overlying mucosa.
- Endoscopic ultrasound (EUS) — defines the origin from the wall and allows targeted sampling where needed.
- CT of the abdomen and pelvis with contrast — for staging and assessing extent; MRI especially for rectal GISTs.
- Histology & immunohistochemistry — positivity for CD117 (KIT) and DOG1 confirms the diagnosis.
- Molecular testing (KIT / PDGFRA) — guides targeted therapy.
For tumours judged resectable, percutaneous biopsy is avoided because of the risk of rupture and seeding; sampling is preferably done endoscopically (EUS) or the diagnosis is confirmed after resection.
What determines their behaviour?
Most GISTs harbour an activating mutation that "drives" the tumour:
- KIT — the commonest, in most cases.
- PDGFRA — in a smaller proportion; certain variants (e.g. D842V) are resistant to imatinib.
- "Wild-type" (e.g. SDH-deficient, NF1-related or BRAF) — rarer, with distinct behaviour.
The risk of recurrence is assessed from three factors: tumour size, mitotic count and location — small bowel GISTs carry a worse prognosis than gastric ones of the same size.
Modern treatment options
Management is individualised and decided within a multidisciplinary team. Surgery is the foundation, while targeted therapy has transformed the prognosis.
For details of the techniques, see the Surgical Services page and the Stomach cancer and Cytoreduction & HIPEC pages.
Surgical Resection
Complete resection (R0) with an intact pseudocapsule and without rupturing the tumour. Lymphadenectomy is not required, as nodal spread is rare. In the stomach a wedge or segmental resection is often sufficient.
Imatinib Therapy
A tyrosine kinase inhibitor given as adjuvant treatment after resection in high-risk tumours, or neoadjuvant to shrink large/borderline tumours and preserve organs. In advanced or resistant disease, sunitinib, regorafenib and ripretinib follow.
Surveillance & Team
Small gastric GISTs (under 2 cm) without worrying features may, in selected cases, be kept under surveillance. Every decision is made within a multidisciplinary team, based on the risk profile.
Frequently asked questions
Is a GIST cancer?
A GIST is not simply divided into benign and malignant; it shows a spectrum of malignant potential. The risk of recurrence and aggressive behaviour is assessed from the tumour size, the mitotic count and the location. Some GISTs are very low risk and others high risk, which also determines treatment.
How does a GIST differ from stomach cancer?
A GIST is a mesenchymal tumour that starts from the interstitial cells of Cajal, within the wall of the stomach (submucosal), and is positive for markers such as KIT (CD117) and DOG1. Gastric adenocarcinoma, by contrast, arises from the mucosa (epithelial in origin). They have different biology, diagnosis and treatment.
Does a GIST need chemotherapy?
Conventional chemotherapy and radiotherapy are largely ineffective in GIST. Their place is taken by targeted therapy with tyrosine kinase inhibitors (imatinib), given as adjuvant treatment in high-risk tumours after resection or in advanced disease. Not every patient needs systemic therapy.
Are lymph nodes removed in GIST surgery?
Not as a rule. GISTs rarely spread to lymph nodes, so systematic lymphadenectomy is not part of the standard operation. The goal is complete resection (R0) with an intact pseudocapsule and without rupturing the tumour.
Can a GIST be removed laparoscopically or robotically?
Yes. For tumours of suitable size and location, laparoscopic or robotic resection is feasible and safe, provided complete resection is achieved without rupturing the pseudocapsule. The choice of approach is individualised to the tumour's characteristics.