1. Most commonly seen in small intestine.
2. The most common histopathologic picture is that of spindle cells and epithelioid cells arranged in storiform pattern.
3. Common in young patients under 30 years of age.
4. Positive for CD117 (c-kit) and CD34.
A. 1, 2, and 3 are correct.
B. 1 and 3 are correct.
C. 2 and 4 are correct.
D. Only 4 is correct.
E. All are correct.
Discussion: Gastrointestinal stromal tumor (GIST) is best defined as cellular spindle cell, epithelioid, or occasionally pleomorphic mesenchymal tumors of the gastrointestinal tract that express the c-kit (CD117) protein as detected by immunohistochemistry.
About 79% of them are also positive for CD34. GISTs may vary in size from small to large and in biological behavior from benign to malignant. They are the most common mesenchymal tumor of the gastrointestinal tract. GISTs are most commonly seen in the stomach (60-70%) and small intestine (20-30%), followed by colon and rectum (less than 5%), and esophagus (less than 5%). Most of them occur in middle aged and eldery patients over 50 years of age.
2. The presence of myxoid stroma in gastrointestinal stromal tumor (GIST) of stomach is a histologic feature associated with benign behavior?
a. true
b. false
Discussion: For gastric stromal tumors, unfavorable prognostic sign include tumor size greater than or equal to 7 cm, high cellularity, mucosal invasion, high nuclear grade, mitotic counts greater than or equal to 5/50 high power fields, mixed cell type, and the presence of a myxoid background and/or absence of stromal hyalinization.
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