OBJECTIVETo study the clinical pathologic and immunohistochemical features of gastrointestinal mesenchymal tumors (GIMTs), and to investigate the value of molecular markers in GIMTs clinical differentiation diagnosis.

METHODSThe clinical and pathological data of 210 cases of GIMTs, collected from Jan. 1987 to Dec. 2005 in our hospital, were investigated retrospectively. GIMTs were rediagnosed by using standard immunostaining technique in paraffin-embedded tissue. The expression level of CD117, CD34, Desmin, SMA and PS100 were detected by immunohistochemical method.

RESULTSAmong 210 cases of GIMTs, 127 cases were Gastrointestinal stromal tumors (GISTs) (60.5%), 33 leiomyomas and leiomyosarcomas (15.7%), 27 neurogenic tumours (12.8%), and 23 miscellaneous tumors (11.0%). The incidences of GIST, leiomyoma and leiomyosarcoma were similar among men and women. Men were more likely to develop neurogenic tumors and miscellaneous tumors than women. Of all the GISTs, 51.2% cases originated from stomach, 19.7% from small intestine, 11.0% from esophagus, 10.2% from colon and rectum. The most common location of leiomyomas and leiomyosarcomas was esophagus (45.5%). The most common location of neurogenic tumors was retroperitoneum (74.1%). Common symptoms of GISTs included digestive tract hemorrhage in 36 cases (28.3%), abdominal pain in 27 cases (21.3%) and abdominal mass in 24 cases (18.9%). Other GIMT cases except GISTs had no first symptom of digestive tract hemorrhage. It was noticed that 79.5% of GISTs had no obvious invasion, and 72.7% of leiomyomas and leiomyosarcomas had no obvious invasion. 33.3% of neurogenic tumors invaded the adjacent organs or tissues. No metastases had been found in other GIMT cases except GISTs. The neoplastic cells of GISTs were composed of various percentage of spindle (72.5%), epithelioid (11.8%) and mixed-type cells (15.7%). The percentage of spindle cells in leiomyomas and leiomyosarcomas was 94. The immunohistochemical results of GISTs showed that the positive rate of CD117 was 93.7%, CD34 was 69.3%, Desmin was 13.4%, SMA was 12.6%, and PS100 was 10.2%. The immunohistochemical results of leiomyomas and leiomyosarcomas showed that the positive rate of Desmin was 78.5%, SMA was 63.6%, while as the expressions of CD117, CD34, and PS100 were negative. Diffuse strong positive staining of PS100 was observed in 88.9% of neurogenic tumor patients.

CONCLUSIONSGISTs are the most common tumors among GIMTs. GISTs are different from neurogenic tumors, leiomyomas and leiomyosarcomas in initial symptom, tumor location, biological behavior and immunophenotype. Immunohistochemistry plays an important role in differentiating GISTs from leiomyomas and neurogenic tumors.