Abstract
To reclassify canine small intestinal and cecal leiomyoma (LM) and leiomyosarcoma (LMS) into smooth muscle and gastrointestinal stromal tumors (GIST) using histologic and immunohistochemical (IH) analysis and to report clinical findings and survival data. Retrospective review of cases. Dogs (n=47) with small intestinal (40 LMS; 7 LM) and 25 dogs with cecal tumors (23 LMS; 2 LM). Clinical and survival data were reviewed. Tissue sections were reevaluated for light-microscopic malignancy criteria and examined for expression of SMA, desmin, vimentin, S-100, and CD117 (KIT) by immunohistochemistry. Reclassification resulted in 2 LM, 9 LMS, 19 GIST, and 17 GIST-like tumors in the small intestine and 23 GIST and 2 GIST-like tumors in the cecum. GIST-like tumors were morphologic and IH identical to GIST but lacked KIT expression. No significant difference in survival was observed for tumor type, location, histologic, or IH characteristics; however, dogs with cecal tumors were significantly older in age, presented more commonly with intestinal perforation and peritonitis, and less commonly with weight loss. Cecal tumors had more histologic malignancy criteria than small intestinal tumors. After excision, 1 and 2 year recurrence-free periods were 80.1% and 67.2% for small intestinal and 83.3% and 61.9% for cecal tumors. Prognosis for intestinal tumors with histologic smooth muscle appearance is good after excision and not related to tumor type, location, histologic, or IH characteristics. Clinical importance could not be demonstrated for reclassification, but may be for future treatment, of intestinal smooth muscle or stromal tumors.
Highlights
IntroductionMost canine gastrointestinal (GI) mesenchymal tumors with smooth muscle appearance have been diagnosed as leiomyoma (LM) or leiomyosarcoma (LMS) by light microscopic examination of hematoxylin and eosin (HE)-stained tissue sections
Of the 47 dogs with small intestinal tumors, 42 had resectable masses treated by partial enterectomy and endto-end anastomosis
One of the most striking conclusions of our study is that tumor type, and histologic and IH characteristics had no significant influence on prognosis after surgical removal
Summary
Most canine gastrointestinal (GI) mesenchymal tumors with smooth muscle appearance have been diagnosed as leiomyoma (LM) or leiomyosarcoma (LMS) by light microscopic examination of hematoxylin and eosin (HE)-stained tissue sections.. Most canine gastrointestinal (GI) mesenchymal tumors with smooth muscle appearance have been diagnosed as leiomyoma (LM) or leiomyosarcoma (LMS) by light microscopic examination of hematoxylin and eosin (HE)-stained tissue sections.2 Clinical characteristics of both tumors have been described for dogs.. From the Departments of Clinical Sciences of Companion Animals and Pathobiology, University of Utrecht, Utrecht, The Netherlands. Financial support for this study was provided by Hill’s Pet Nutrition Inc., the Department of Pathobiology and the DOG Foundation, Department of Clinical Sciences of Companion Animals, University of Utrecht, Utrecht, the Netherlands. Based on IH analysis, tumors from true smooth muscle origin can be differentiated from stromal tumors Using immunohistochemical (IH) analysis, tumors identified by histologic evaluation of HE-stained specimens as being of smooth muscle origin are a heterogeneous group of mesenchymal tumors that may not express smooth muscle markers. In human and veterinary patients, IH and ultrastructural studies of these tumors demonstrate differentiation toward either smooth muscle (myogenic), or neural tissue (neurogenic), a combination of both (mixed), or undifferentiated tissue (anaplastic). Based on IH analysis, tumors from true smooth muscle origin can be differentiated from stromal tumors
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