Revision of gastrointestinal mesenchymal tumors.

BACKGROUND: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the gastrointestinal (GI) tract. The advent of target therapy (imatinib mesylate) for GISTs increases the importance of pathologic diagnosis. The previous diagnosis with smooth muscle tumor (leiomyoma or leiomyosarcoma) and nerve sheath tumor (schwannoma) become GISTs after the study with CD117 immunohistochemistry accompanying conventional histologic study in many series. OBJECTIVE: To identify the incidence of GISTs in the patients who were previously diagnosed with smooth muscle or nerve sheath tumors. The histology and immunoreactivity of both newly found and previously diagnosed with GISTs are also studied MATERIAL AND METHOD: A retrospective database identified all patients seen from 1998 to 2006. Patients with mesenchymal tumors of the GI tract and intraabdominal extragastrointestinal tract were selected, 53 cases in total. Clinical and pathological data, treatment, and outcome were analyzed RESULTS: After revision, the total number of GISTs is 42 cases. There were 33 cases previously diagnosed with leiomyosarcoma that became the diagnosis with GISTs (31 cases or 93.9%), due to CD117 positivity. Most of GISTs cases had spindle cell type (26 cases, 61.9%) and only the colon and omentum had predominant mixed cell type. CONCLUSION: GISTs are the most common mesenchymal neoplasm of the stomach and small intestine and are relatively less frequent at other gastrointestinal sites. An increasing awareness of their histologic, immunophenotypic, and molecular features coupled with an evolving understanding of their histogenesis is facilitating our ability to identify these tumors.