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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}, {{AJL}} {{Alison}}
|QuestionAuthor={{Rim}} (Reviewed by {{AJL}} and {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Pathology
|MainCategory=Pathology
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|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Gastrointestinal
|SubCategory=Gastrointestinal
|Prompt=A 62-year-old male presents to the physician's office with complaints of abdominal pain, which has been worsening over the past four months. The dull pain is localized in the epigastric area and persistently increasing in intensity, independently from food intake or change in posture. Upon further questioning, he describes symptoms of increasing fatigue and weight loss. A CT scan displays a mass in the stomach and an endoscopy-guided biopsy of the mass reveals clusters of thin, elongated spindle cells. Which of the following immunohistochemistry findings is most helpful in diagnosing the type of tumor in this patient?
|Prompt=A 62-year-old man presents to the physician's office with complaints of worsening abdominal pain over the past four months. The pain is described as dull and localized in the mid-epigastric region. The patient denies any association between his pain and food intake or posture. Upon further questioning, he describes symptoms of increasing fatigue and recent unintentional weight loss. An abdominal CT scan shows a gastric mass, and an endoscopy-guided biopsy of the mass reveals clusters of thin, elongated, spindle cells. Immunohistochemistry of this patient's tumor is most likely to reveal expression of which protein?
|Explanation=The patient's symptoms of epigastric pain, fatigue, and weight loss, in conjunction with the CT finding of a mass in the stomach, points towards the diagnosis of malignancy. The spindle cells on pathology are often diagnostic for a [[gastrointestinal stromal tumor]] (GIST), which can be confirmed by positive immunohistochemistry for C-kit.
|Explanation=Gastrointestinal stromal tumor (GIST) is a rare non-epithelial neoplasm of the GI tract, the mesentary, or the omentum. The majority of GIST tumors are spindle cell tumors that may be either malignant or benign. Most stromal tumors stain positively for C-Kit/CD117 (>90%), CD34, muscle-specific actin, smooth muscle actin, S-100, and desmin. Patients with GIST may be asymptomatic or have non-specific GI symptoms. This patient's symptoms of dull epigastric pain, fatigue, and weight loss, in conjunction with the CT finding of a mass in the stomach, are suggestive of malignancy. Characteristically, the pathogenesis of GIST tumors involves a gain-of-function mutation in the ''KIT'' proto-oncogene, which encodes a transmembrane receptor for stem cell factor that includes a tyrosine kinase component in its intracytoplasmic region.
|AnswerA=C-kit
|AnswerA=C-kit
|AnswerAExp=[[C-kit]] oncogene is associated with [[GIST]]. [[C-kit]] gene encodes the human homolog of the proto-oncogene c-kit, also called CD117.
|AnswerAExp=Expression of [[C-kit]] is associated with [[GIST]].  
|AnswerB=Ret
|AnswerB=Ret
|AnswerBExp=The [[Ret gene|Ret oncogene]] is often associated with [[MEN|MEN syndrome]], type IIa and IIb.
|AnswerBExp=Expression of Ret protein is associated with multiple endocrine neoplasia (MEN) 2A and 2B syndromes.
|AnswerC=Abl
|AnswerC=Abl
|AnswerCExp=The [[Abl gene|Abl oncogene]] is often associated with CML.
|AnswerCExp=Expression of Ab1 is often associated with chronic myelogenous leukemia (CML).
|AnswerD=Ras
|AnswerD=Ras
|AnswerDExp=The [[Ras]] oncogene is often associated with colon carcinoma.
|AnswerDExp=Expression of Ras is associated with colon adenocarcinoma.
|AnswerE=C-myc
|AnswerE=C-myc
|AnswerEExp=[[C-myc]] is associated with [[Burkitt's lymphoma]].
|AnswerEExp=Expression of [[C-myc]] is associated with [[Burkitt's lymphoma]].
|EducationalObjectives=[[C-kit]], also called [[CD 117]], is often associated with [[gastrointestinal stromal tumor]]s (GIST).
|EducationalObjectives=Gastrointestinal stromal tumor (GIST) is a rare non-epithelial neoplasm of the GI tract, the mesentary, or the omentum. The majority of GIST tumors are spindle cell tumors that may be either malignant or benign. Most stromal tumors stain positively for C-Kit/CD117
|References=First Aid 2014 page 232
|References=Din OS, Woll PJ. Treatment of gastrointestinal stromal tumor: focus on imatinib mesylate. Ther Clin Risk Manag. 2008;4(1):149-62.<br>
First Aid 2014 page 232
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Cancer, GIST, Gastrointestinal stromal tumor, Genetics, Histology, Marker, Mutation,  
|WBRKeyword=Cancer, GIST, Gastrointestinal stromal tumor, Marker, Mutation, KIT, C-kit, Proto-oncogene, Immunohistochemistry
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 21:30, 7 November 2014
Author [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz [2] and Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pathology
Sub Category SubCategory::Gastrointestinal
Prompt [[Prompt::A 62-year-old man presents to the physician's office with complaints of worsening abdominal pain over the past four months. The pain is described as dull and localized in the mid-epigastric region. The patient denies any association between his pain and food intake or posture. Upon further questioning, he describes symptoms of increasing fatigue and recent unintentional weight loss. An abdominal CT scan shows a gastric mass, and an endoscopy-guided biopsy of the mass reveals clusters of thin, elongated, spindle cells. Immunohistochemistry of this patient's tumor is most likely to reveal expression of which protein?]]
Answer A AnswerA::C-kit
Answer A Explanation [[AnswerAExp::Expression of C-kit is associated with GIST.]]
Answer B AnswerB::Ret
Answer B Explanation AnswerBExp::Expression of Ret protein is associated with multiple endocrine neoplasia (MEN) 2A and 2B syndromes.
Answer C AnswerC::Abl
Answer C Explanation AnswerCExp::Expression of Ab1 is often associated with chronic myelogenous leukemia (CML).
Answer D AnswerD::Ras
Answer D Explanation AnswerDExp::Expression of Ras is associated with colon adenocarcinoma.
Answer E AnswerE::C-myc
Answer E Explanation [[AnswerEExp::Expression of C-myc is associated with Burkitt's lymphoma.]]
Right Answer RightAnswer::A
Explanation [[Explanation::Gastrointestinal stromal tumor (GIST) is a rare non-epithelial neoplasm of the GI tract, the mesentary, or the omentum. The majority of GIST tumors are spindle cell tumors that may be either malignant or benign. Most stromal tumors stain positively for C-Kit/CD117 (>90%), CD34, muscle-specific actin, smooth muscle actin, S-100, and desmin. Patients with GIST may be asymptomatic or have non-specific GI symptoms. This patient's symptoms of dull epigastric pain, fatigue, and weight loss, in conjunction with the CT finding of a mass in the stomach, are suggestive of malignancy. Characteristically, the pathogenesis of GIST tumors involves a gain-of-function mutation in the KIT proto-oncogene, which encodes a transmembrane receptor for stem cell factor that includes a tyrosine kinase component in its intracytoplasmic region.

Educational Objective: Gastrointestinal stromal tumor (GIST) is a rare non-epithelial neoplasm of the GI tract, the mesentary, or the omentum. The majority of GIST tumors are spindle cell tumors that may be either malignant or benign. Most stromal tumors stain positively for C-Kit/CD117
References: Din OS, Woll PJ. Treatment of gastrointestinal stromal tumor: focus on imatinib mesylate. Ther Clin Risk Manag. 2008;4(1):149-62.
First Aid 2014 page 232]]

Approved Approved::Yes
Keyword WBRKeyword::Cancer, WBRKeyword::GIST, WBRKeyword::Gastrointestinal stromal tumor, WBRKeyword::Marker, WBRKeyword::Mutation, WBRKeyword::KIT, WBRKeyword::C-kit, WBRKeyword::Proto-oncogene, WBRKeyword::Immunohistochemistry
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