Gastroinetstinal stromal tumors: Two clinical cases = [Tumori stromali gastroenterici (GIST): Due casi clinici]

Gastrointestinal stromal tumor (GIST) is a mesenchymal spindle cell (70-80%) or epithelioid (20-30%) neoplasm. “GIST” is rela- tively new therminology, theese would once have been called leiomyomas, leiomyoblastomas and/or leiomyosarcomas. GISTs occur more often in stomach (50%), followed by small bowel (30%; ileum>jejunum>duodenum), the colon-rectum and the esophagus (20%). The diagnosis is based on a positive c-kit (CD117) stain, which is a tyrosine kinase growth factor recep- tor. Gain of function mutations of c-kit gene are found in many GISTs and these mutations result in costitutive activation of c-kit protein that stimulates proliferation of GIST tumor cells and may inhibit apoptotic cell death. Some of these tumors respond drammatically to STI571 (Gleevec), which is highly effective in vit- ro in reducing c-kit tyrosine-kinase activity. The majority are benign, 10-30% are malignant. The differentiation is made accord- ing to the number of mitoses counted during hystological exam- ination. Several factor increase the likelihood of malignancy in GISTs. Theese include extragastric location, size greater than 5 cm, central necrosis extention into adjacent organs and metastases (occurring in liver and peritoneum much more frequently than in the lung, bone or lymphonodes). First choice treatment is still nowadays surgical excission though medical progresses will prob- ably change in the future the therapeutic approach.