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Presented by Ralph Hruban, M.D. and prepared by Bahram R. Oliai, M.D.
Case 1: This 75-year-old male presented with abdominal pain.
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1. Question
Week 65: Case 1
This 75-year-old male presented with abdominal pain. A CT Scan revealed an 11cm mass in the stomach./images/01-48998a.jpg
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/images/01-48998d.jpgCorrect
Answer: Malignant gastrointestinal stromal tumor
Histology: This high-grade spindle cell neoplasm of the stomach was remarkable for its large size (11 cm), cellularity and high mitotic activity. An immunostain for C-Kit (CD117) was positive as was an immunostain for CD34. An immunostain for S-100 protein was negative.
Discussion: Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms that show differentiation similar to that seen in the interstitial cells of Cajal, the pacemaker cells of the gastrointestinal tract. GISTs can be predominately spindle shaped to epithelial in character. Almost all GISTs express C-Kit (CD117) and CD34. C-kit encodes for a growth factor receptor with tyrosine kinase activity. The expression of C-kit by a spindle cell neoplasms in the gastrointestinal tract helps resolve the histopathological differential diagnosis between GISTs and other spindle cell neoplasms. C-kit is also a target for directed therapies (see Leuk. Res. 2001, 25:571-6). Although no specific histologic criteria have yet been identified that can unambiguously predict biological behavior, the large size and high mitotic rate of this neoplasm suggest it is likely to follow a malignant course.
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Answer: Malignant gastrointestinal stromal tumor
Histology: This high-grade spindle cell neoplasm of the stomach was remarkable for its large size (11 cm), cellularity and high mitotic activity. An immunostain for C-Kit (CD117) was positive as was an immunostain for CD34. An immunostain for S-100 protein was negative.
Discussion: Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms that show differentiation similar to that seen in the interstitial cells of Cajal, the pacemaker cells of the gastrointestinal tract. GISTs can be predominately spindle shaped to epithelial in character. Almost all GISTs express C-Kit (CD117) and CD34. C-kit encodes for a growth factor receptor with tyrosine kinase activity. The expression of C-kit by a spindle cell neoplasms in the gastrointestinal tract helps resolve the histopathological differential diagnosis between GISTs and other spindle cell neoplasms. C-kit is also a target for directed therapies (see Leuk. Res. 2001, 25:571-6). Although no specific histologic criteria have yet been identified that can unambiguously predict biological behavior, the large size and high mitotic rate of this neoplasm suggest it is likely to follow a malignant course.