The prevalence of gastrointestinal tumors in dogs is low and has been reported as 3% of all neoplasms in that species.1 Leiomyosarcomas are reported to be the most common sarcoma of the canine intestinal tract and comprise approximately 10% to 30% of all intestinal tumors in dogs.2–6 Recently, the advent of advanced immunohistochemical staining techniques has led to reclassification of GILMSs in human medicine. It has been recognized that tumors previously categorized as GILMSs are not composed entirely of smooth muscle but are principally derived from ICCs.7–9 Interstitial cells of Cajal are the pacemaker cells of the gastrointestinal tract and regulate intestinal motility and peristalsis. The ICC-derived tumors have been renamed GISTs. Gastrointestinal stromal tumors are immunohistochemically distinguishable from GILMSs or true smooth muscle tumors on the basis of expression of c-kit (CD-117). Leiomyosarcomas do not express the c-kit protein. The c-kit protein is a transmembrane receptor with a tyrosine kinase component. Most GISTs have activating c-kit mutations that are thought to be the driving force in GIST oncogenesis.10–16 Gastrointestinal stromal tumors have not only been identified in humans but have also been recently detected in equids, nonhuman primates, and dogs.17–22 Some canine mast cell tumors also express c-kit mutations.23,24 The purpose of the study reported here was to reexamine (via immunohistochemical techniques) canine tissue samples that had been previously classified as GILMSs, identify and differentiate GISTs from GILMSs, and compare the biological behavior and clinical course of GISTs and GILMSs in dogs. To the authors' knowledge, no reports of naturally occurring GISTs in a hospital population of client-owned dogs have been published previously.
Interstitial cell of Cajal
Gastrointestinal stromal tumor
Smooth muscle actin
SAS software, version 9.1, SAS Institute Inc, Cary, NC.
Adriamycin, Ben Venue Laboratory Inc, Bedford, Ohio.
Cisplatin, Sicor Pharmaceutical Inc, Irvine, Calif.
Gleevec, Novartis International AG, Basel, Switzerland.
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