RESUMEN
<p><b>OBJECTIVE</b>To study the histogenesis and pathological characteristics of gastrointestinal stromal tumors (GIST) and GIST type stromal tumor (ST) beyond the gastrointestinal tract.</p><p><b>METHODS</b>A retrospective study was carried out on leiomyoma, leiomyosarcoma and neurilemoma (46 cases in gastrointestinal tract and l3 cases in urinary tract and perineal area). 4 antibodies (CD117, CD34, SMA, S-100) were used for immunohistochemical staining.</p><p><b>RESULTS</b>Among 45 cases of GIST, the positive rate of CD117 and CD34 was 93.3% and 88.9% respectively. Among 12 cases of GIST type ST beyond the gastrointestinal tract, the positive rate of CD117 and CD34 was 83.3% and 75.0% respectively. In 2 cases (1 in gastrointestinal tract) of leiomyomas, both CD117 and CD 34 were negative in tumor cells, while SMA was extensively positive.</p><p><b>CONCLUSIONS</b>CD117 and CD34 positivity are the most valuable factors in diagnosing ST. Both GIST and GIST type ST beyond the gastrointestinal tract are considered originating from a proto-interstitial stem cell with disoriented differentiation.</p>