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WHO Classification of Tumours
Gastrointestinal stromal tumor, malignant
Colon and rectum


The term gastrointestinal stromal tumour (GIST) is used for a specific group of tumours comprising the majority of gastrointestinal mesenchymal tumours, including those previously termed leiomyoma, cellular leiomyoma, leiomyoblastoma and leiomyosarcoma
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Hamilton SR, Aaltonen LA (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Digestive System.
3rd Edition
IARC Press: Lyon 2000

. Rare cases involving tissues outside the gastrointestinal tract have also been reported (extragastrointestinal gastrointestinal stromal tumors). GIST are KIT-expressing and KIT-signaling-driven mesenchymal tumors that repsond favourably to treatment with the KIT tyrosine kinase inhibitor imatinib mesylate / Gleevec
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Druker BJ (2004)
Imatinib as a paradigm of targeted therapies.
Adv Cancer Res 91: 1-30

Malignant GIST is a subtype of gastrointestinal stromal tumor characterized by large size (diameter greater than 10cm) and more than 5 mitotic figures per 50 high power fields.

GISTs of the colon and rectum
GISTs are very rare in the colon (about 1% of all GISTs) and have a predilection for the sigmoid. However, microscopic GISTs have been detected in 0.2% of retrospectively examined sigmoid-colon resections. Rectal GISTs comprise 4% of all GISTs and occur in any segment. These tumours vary from incidentally detected small mural nodules to large, complex pelvic masses that can cause intestinal obstruction or gastrointestinal bleeding. Those with anterior extension can abut the prostate gland and clinically simulate prostate cancer

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Agaimy A, WŁnsch PH, Dirnhofer S, Bihl MP, Terracciano LM, Tornillo L (2008)
Microscopic gastrointestinal stromal tumors in esophageal and intestinal surgical resection specimens: a clinicopathologic, immunohistochemical, and molecular study of 19 lesions.
Am J Surg Pathol 32: 867-73

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Hassan I, You YN, Shyyan R, Dozois EJ, Smyrk TC, Okuno SH, Schleck CD, Hodge DO, Donohue JH (2008)
Surgically managed gastrointestinal stromal tumors: a comparative and prognostic analysis.
Ann Surg Oncol 15: 52-9

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Miettinen M, Furlong M, Sarlomo-Rikala M, Burke A, Sobin LH, Lasota J (2001)
Gastrointestinal stromal tumors, intramural leiomyomas, and leiomyosarcomas in the rectum and anus: a clinicopathologic, immunohistochemical, and molecular genetic study of 144 cases.
Am J Surg Pathol 25: 1121-33

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Miettinen M, Sarlomo-Rikala M, Sobin LH, Lasota J (2000)
Gastrointestinal stromal tumors and leiomyosarcomas in the colon: a clinicopathologic, immunohistochemical, and molecular genetic study of 44 cases.
Am J Surg Pathol 24: 1339-52

Most colonic GISTs are advanced tumours when detected, and have a poor prognosis. The behaviour of rectal GISTs is often aggressive, and even small tumours of < 2 cm in size with mitotic activity can recur and metastasize. Pelvic extension and liver metastasis is common, and bone metastases may develop more often than in gastric and small-intestinal GISTs

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Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010