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Int J Clin Exp Pathol 2010;3(2):162-168

Original Article
Gastrointestinal stromal tumor of the digestive organs: a histopathologic study of 31
cases in a single Japanese institute

Tadashi Terada

Department of Pathology, Shizuoka City Shimizu Hospital, Shizuoka, Japan

Abstract: The author herein reports histopathologic features of 31 surgical cases of gastrointestinal stromal tumor (GIST) of the digestive
organs. The 31 cases of GIST were diagnosed in our pathology laboratory. They consisted of 24 cases of gastric GIST, 1 case of hepatic GIST,
1 case of small intestinal GIST, 4 cases of colon GIST, and 1 case of rectal GIST. The age of the patients ranged from 56 year to 84 years with
a mean of 71 years. Male to female ratio was 21:10. The presenting symptoms were gastrointestinal bleeding in 13 cases, abdominal pain
and discomfort in 13 cases, and asymptomatic in 5 cases. Endoscopy and imaging modalities including US, CT and MRI were useful to detect
the tumors in all cases, and biopsies confirmed the GIST diagnosis in 21 cases. The size of GIST ranged from 1 cm to 12 cm with a mean of
4.3 cm. Grossly, 23 cases were submucosal tumors, 6 serosa-side tumors, 1 solid tumor in the liver, and 1 rectal polyp. Histologically, 28
cases were of spindle cell type and 3 of epithelioid type. According to mitotic counts and tumor size, the malignant risk was very low in 4 cases,
low in 14 cases, intermediate in 9 cases, and high in 4 cases. Immunohistochemically, all cases were positive for KIT and vimentin, 30 cases
for CD34, and 4 cases for α-smooth muscle actin. None were positive for desmin and S100 protein. Ki-67 labeling ranged from 2% to 18%.
P53 protein was negative in all cases. PDGFRA was positive in 20 cases among 24 cases examined. Genetic analysis using PCR-direct
sequencing method was performed in 5 GISTs; all the 5 GISTs showed point mutations or deletions in KIT gene, but did not in PDGFRA
gene. The 5 cases of GIST were positive for PDGFRA protein, suggesting that PDGFRA overexpression is not associated with PDGFRA gene
mutations. Four of the 31 cases showed metastases. The chemotherapy was imatinib mesylate in 6 cases, and none in 25 cases. Four cases
of high risk died of GIST, and 27 cases are alive now without tumors. (IJCEP906001).

Key words: GIST, desmin, KIT, PDGFRA, clinicopathology, immunohisology, genetics

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Address all correspondence to:
Tadashi Terada, MD, PhD
Department of Pathology
Shizuoka City Shimizu Hospital
Miyakami 1231 Shimizu-
Ku, Shizuoka 424-8636, Japan.
Tel: +81-543-36-1111
Fax: +81-543-36-1173