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.