WBR0246

Author	[[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Gastrointestinal
Prompt	[[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?]]
Answer A	AnswerA::C-kit
Answer A Explanation	[[AnswerAExp::C-kit oncogene is associated with GIST. C-kit gene encodes the human homolog of the proto-oncogene c-kit, also called CD117.]]
Answer B	AnswerB::Ret
Answer B Explanation	[[AnswerBExp::The Ret oncogene is often associated with MEN syndrome, type IIa and IIb.]]
Answer C	AnswerC::Abl
Answer C Explanation	[[AnswerCExp::The Abl oncogene is often associated with CML.]]
Answer D	AnswerD::Ras
Answer D Explanation	[[AnswerDExp::The Ras oncogene is often associated with colon carcinoma.]]
Answer E	AnswerE::C-myc
Answer E Explanation	[[AnswerEExp::C-myc is associated with Burkitt's lymphoma.]]
Right Answer	RightAnswer::A
Explanation	[[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. Educational Objective: C-kit, also called CD 117, is often associated with gastrointestinal stromal tumors (GIST). References: First Aid 2014 page 232]]
Approved	Approved::Yes
Keyword	WBRKeyword::Cancer, WBRKeyword::GIST, WBRKeyword::Gastrointestinal stromal tumor, WBRKeyword::Genetics, WBRKeyword::Histology, WBRKeyword::Marker, WBRKeyword::Mutation
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::