GASTROINTESTINAL STROMAL TUMORS OF THE ANORECTUM——A SPECIAL ENTITY: GISTs OF THE ANORECTUM

Objective: Until recently gastrointestinal stromal tumor (GIST) has been separated from other mesenchymal neoplasms and categorized as a special entity. Morphology of tumor cells and immunohistochemical findings with CD117 are crucial in the pathological diagnosis of GISTs. Newly developed drug imatinib mesylate (formerly called STI571) has been proved effective for GISTs. The distinction of GISTs and other mesenchymal tumors has great clinical significance, especially for lesions located in the anorectum. Methods: The authors searched the database of Peking University, School of Oncology for patients with anorectal neoplasms treated from January 1995 to June 2002. Information of 12 patients with anorectal mesenchymal tumors was collected. The patients were reevaluated and discussed according to current criteria of GISTs with clinical data and immunohistochemical findings. Results: Six patients (including 3 males) were finally diagnosed as anorectal GISTs. The median age of those patients was 59.5 years (27～69). The symptoms were not specific. Three cases with original diagnosis of leiomyoma or leiomyosarcoma were actually GISTs. A total of six anorectal GISTs was found comprising about 1.06% of patients with anorectal neoplasmas in the same period. Besides CD117, CD34 and vimentin were also expressed in majority of these patients. Five of the six patients underwent surgical resection one of which received neoadjuvant chemotherapy before resection. Conclusion: Anorectal GISTs should be considered as a special entity using current diagnostic criteria. Surgical resection remains the primary therapeutic strategy. Neoadjuvant imatinib mesylate may be helpful in sphincter-sparing operations and improvement of the quality of life for these patients.