A case of gastrointestinal stromal tumor arising in the external anal sphincter muscle

Abstract

We present a case of gastrointestinal stromal tumor (GIST) arising in the perianal region. A 78-year-old Japanese man who had suffered from an asymptomatic buttock tumor from April 2006 was seen at our hospital because of anal discomfort and dyschezia in December 2006. He had undergone treatments for a perianal abscess and an anal fistula. The buttock tumor had grown gradually and a possibility of malignancy could not be ruled out, so the tumor was surgically excised on March 16th 2006. The excised tumor was 6.0cm in diameter and was composed of spindle-shaped atypical cells. In histopathological examinations, both c-kit and CD34 antigens were positive and the tumor was diagnosed as GIST. The patient has been well without any recurrent signs in these 26 months.