<prompt> Which of the following markers is specific for gastro-intestinal stomal tumor GIST -CD 117CD 34CD 23S-100  <response>: lmmunohistochemistry o Following markers are present in GISTs: i CD 117 c kit --95 ii CD 34 -- 70 iii Smooth muscle actin 5 CD 117 c kit is considered the most specific marker o 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. REF: ROBBINS pathology 10th edition 