Immuno-marker for GIST is?
**Core Concept:** Gastrointestinal stromal tumors (GISTs) are a type of sarcoma that originates from the interstitial cells of Cajal, which are pacemaker cells in the gastrointestinal tract responsible for regulating gut motility. GISTs are characterized by the presence or absence of specific mutations, particularly KIT proto-oncogene mutations (KIT mutations) or platelet-derived growth factor receptor alpha (PDGFRA) mutations. Immuno-markers are used to identify these mutations and help in diagnosing GISTs.
**Why the Correct Answer is Right:** The correct answer, DOG1, is an immuno-marker used to identify the presence of KIT mutations in GISTs. DOG1 is a protein expressed in normal and neoplastic cells of the gastrointestinal tract, particularly in the cells of Cajal, and is a useful marker for diagnosing GISTs.
**Why Each Wrong Option is Incorrect:**
A. CD117 (also known as c-KIT) is a proto-oncogene involved in cell differentiation and proliferation. Mutations in CD117 gene are associated with GISTs, and detecting CD117 expression is essential in diagnosing GISTs. However, this option is incorrect because CD117 is not an immuno-marker, but rather a gene mutation.
B. CD34 is a cell surface protein that is expressed in various types of tumors, including GISTs. However, CD34 is not specific for GISTs, and its presence does not confirm the diagnosis of GIST. This option is incorrect because it is not an immuno-marker specific to GISTs.
C. CD117 (also known as c-KIT) is a proto-oncogene involved in cell differentiation and proliferation. However, this option is incorrect because CD117 is not an immuno-marker, but rather a gene mutation. Detecting CD117 expression is essential in diagnosing GISTs, but this option is incorrect due to the same reason as option A.
**Clinical Pearl:** DOG1 immuno-marker is essential for diagnosing GISTs, as it identifies the presence of KIT mutations, which are responsible for the development of GISTs. DOG1 is a useful marker for diagnosing GISTs, especially when CD117 is not expressed or is expressed at low levels.