Most common site of GIST is -

Ans. is 'd' i.e., Stomach Gastrointestinal stromal tumors (GlSTs)o GISTs are the most common mesenchymal neoplasm of gastrointestinal tumor.o GIST represents a distinct group of gastrointestinal tumors that originate from the interstial cells of cajal which control gastrointestinal peristalsis.o GISTs can occur anywhere in the gastroinstestinal tract; the most common site being the stomach followed by small intestine.Stomach-50-70%Small intestine -20-30%Colon & rectum-5-15%Esophagus -<5% Immunohistochemistrvo Following markers are present in GISTs:i) CD 117 (c kit)- 95%ii) CD 34-70%iii) Smooth muscle actin- 5%o CD 117 (c kit) is considered the most specific markero CD 117 (c kit) immunoreactivity is the best defining feature of GISTs distinguishing them from true smooth muscle tumors (leiomyoma) and tumors arising from neural crest.o Although CD 117 (c kit) is considered the most specific marker for GIST, it is not pathognomonic of GIST as other tumors may also express CD 117. These tumors include mast cell tumor, germ cell tumors (seminomas), leukemias, malignant melanoma, angiolipomas, and some sarcomas.o Gastrointestinal stromal tumors (GIST) originate from the interstitial cells of Cajal.