Gastrointestinal stromal tumors: Review on morphology, molecular pathology, diagnostics, prognosis and treatment options

Gastrointestinal stromal tumors (GISTs) are the most common non-epithelial mesenchymal tumors of the gastrointestinal tract. GISTs represent a specific group of mesenchymal tumors with uncertain biological behaviors. These tumors are assumed to originate from progenitor cells, usually unable to self-regenerate, which differentiate towards Cajal cells. Apart from common GISTs that occur predominantly in adulthood, a heterogeneous group of tumors has been described that are morphologically identical with GIST, but have a specific clinical presentation and biological properties. Approximately 30% of newly diagnosed GISTs are malignant or have a high potential for malignancy. Currently, GISTs are routinely identified with histological, immunohistochemical, and molecular genetic assays. However, clinical diagnoses, particularly of small or intramural GISTs, might be difficult. The most useful techniques for imaging and monitoring disease progression are endoscopic examinations and fused PET/CT imaging. Surgical treatment is the first-line treatment and the only method that might lead to full remission in patients with a primary GIST. There is currently no consensus on the issues of whether to perform resections in patients with positive margins or resections of metastases. Endoscopic resection could represent a relatively simple and less aggressive alternative as compared to traditional surgery in the treatment of small sized GISTs. Biological therapy with imatinib mesylate is recommended for patients with newly diagnosed, locally advanced, inoperable, or metastasizing gastrointestinal GISTs that express the c-KIT protein. Treatment may reduce a primary tumor to a size small enough for surgical excision. Current research is focusing on the development of new therapies for the treatment of advanced disease and/or disease prophylaxis.