Gastro-Intestinal Stromal Tumour (GIST)
Gastrointestinal Stromal Tumours (GIST) are rare tumours of the digestive system. They are most commonly found in the stomach, but can occur anywhere along the intestinal tract and even in the mesentry, omentum, retroperitoneum and gallbladder.
The tumour arises from special cells know as interstitial cells of Cajal, which function as pacemaker to regulate the contraction of the intestines to move food and fluid along.
It is important to differentiate GIST from other more common tumours of the intestinal tract as treatment and outlook are very different.
There is no specific risk factor for the development of GIST, though there are rare instances of a genetic predisposition.
Many early, small GIST do not produce symptoms and are usually detected incidentally, for example on gastroscopy for symptoms of “gastric” discomfort or when a CT scan is done for investigation of urinary stones.
Larger GIST may cause symptoms of:
- Passing of black tarry stools
- Lethargy (from blood loss)
- Vomiting and abdominal distension from intestinal obstruction
- Abdominal pain
- Mass in the abdomen
- Loss of appetite and weight
When a tumour is suspected or found incidentally, investigations are done to confirm the diagnosis as well as to assess the spread of the tumour.
- Gastroscopy for tumours in the stomach and duodenum
- Colonoscopy to evaluate growths found in the colon
- Capsule endoscopy (a capsule with a camera transmitting images of the lumen of the intestine) for tumours in the small intestine
- Barium studies (special X-rays with swallowed contrast)
The spread of the tumour can be assessed with CT, MRI or PET scans.
In order to confirm the diagnosis, a biopsy of the tumour may be required. This can be achieved via:
- Percutaneous biopsy (biopsy through the skin)
- Endoscopic ultrasound guided biopsy
- Laparoscopic surgical biopsy (minimally invasive keyhole surgery)
- Open surgical biopsy
The behaviour of GIST vary widely and can range from benign growths to malignant cancers.
Surgery is recommended for:
- Tumours causing symptoms
- Tumours where diagnosis of cancer is suspected or confirmed
Surgery may be combined with targeted therapy (similar to chemotherapy). The two drugs used as targeted therapy of GIST are imatinib and sunitinib, both of which are taken orally.
The stomach is the most common site for GIST, and many of such tumours are amenable to removal by laparoscopic or keyhole techniques.