Gastrointestinal stromal tumours (GISTs) are rare tumours of the gastrointestinal tract. Although GISTs can occur along the length of the gastrointestinal tract from the oesophagus to the anus, the majority (60% to 70%) arise in the stomach. Most GISTs are associated with overexpression of the tyrosine kinase receptor KIT (CD117), which is thought to promote tumour growth or to inhibit tumour cell death through a signal transduction pathway involving stem cell factor.
Approximately one-third of people with GISTs are asymptomatic during the early stages of the disease. Signs and symptoms can include abdominal discomfort or pain, a feeling of abdominal fullness and the presence of a palpable mass. People have more severe symptoms when tumours metastasise or when they become large, rupture and bleed or obstruct the gastrointestinal tract. In metastatic disease, systemic symptoms such as fever, night sweats and weight loss are common.
Approximately 900 people are newly diagnosed with GISTs in the UK each year. Although GISTs can occur at any age, the usual age of presentation is between 50 and 70 years. Diagnosis of GIST is confirmed by clinical presentation and tissue biopsy to determine the histological characteristics of the tumour, including expression of the KIT (CD117) protein. Approximately 4% of GISTs have characteristic clinical and morphological features, but do not express the KIT (CD117) protein.
The size, growth rate and location of the tumour often influence prognosis. Without treatment GISTs progress and will eventually metastasise. Prognosis depends on whether the tumour can be resected, which is the primary treatment for GISTs. Only 50% of GISTs are resectable at presentation. Conventional cytotoxic chemotherapy and radiotherapy are ineffective in treating advanced or metastatic GISTs. Similarly, surgery to treat advanced or metastatic GISTs is not recommended unless there is an immediate clinical need, such as to remove an obstructing tumour.