11 January 2006 Case of the Week #33


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We thank Dr. Michael Constantinescu, Armstrong County Memorial Hospital, Kittanning, Pennsylvania (USA) for contributing this case. We invite you to contribute a Case of the Week by sending an email to

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Case of the Week #33


Clinical History


A 48 year old man with GI symptoms was discovered to have a 4 cm stomach tumor.


Micro images (low to high power): image #1; #2; #3


Immunostains: CD117-low power; CD117-high power


What is your diagnosis?


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Gastrointestinal stromal tumor (GIST) of stomach




In 1983, Mazur and Clark suggested that GIST tumors, once thought to be derived from smooth muscle, might have a neural origin (AJSP 1983;7:507). Subsequent work has demonstrated that these tumors differentiate along the lines of the interstitial cell of Cajal, involved in the gut pacemarker activity that regulates peristalsis.


Two thirds of all GIST tumors arise in the stomach, where their behavior is usually benign. In the stomach, poor prognostic factors are location in the fundus or GE junction, coagulative necrosis, ulceration and mucosal invasion (AJSP 2005;29:52). Morphology for tumors from various sites has also been used to predict behavior, with pure or mixed cellular spindle cell or epithelioid cell patterns associated with benign behavior and other patterns considered not to be benign (AJSP 2002;26:705)


These tumors are immunoreactive for CD117 / KIT (Hum Path 2002;33:669), as well as CD34. Of note, the interstitial cell of Cajal is also CD117+ and CD34+.


A novel therapy for metastatic or unresectable CD117+ GIST tumors, as well as CML and other CD117+ tumors, is STI-571 (Gleevec, imatinib mesylate), an inhibitor of receptor tyrosine kinase. It inhibits constitutive activation of mutated KIT, and confirmation of KIT immunoexpression is required for its use (Pathol Int 2006;56:1). In the present case, with no evidence of metastatic tumor, treatment consisted only of tumor excision.


Additional references: Mod Path 2003;16:366


Nat Pernick, M.D.
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