EPITHELIOID GASTRIC STROMAL TUMORS (LEIOMYOBLASTOMAS) - A STUDY OF 55CASES

Background. Epithelioid gastric stromal tumors form a distinct histolo gical subset of gastric tumors whose malignant potential and prognosis are controversial. Methods. Fifty-five patients with epithelioid gast ric stromal tumors accounted for 11.5% of patients undergoing definiti ve operations for gastric stromal tumors from 1960 to 1986. Medical re cords and pathology slides were reviewed and immunohistochemical stain ing and flow cytometry were performed. The Kaplan-Meier method was use d to estimate survival. Survival curves were compared with log-rank te sts and Cox proportional hazards model. Results. Of the 55 tumors, 40 were benign and 15 (27%) were malignant. Mean follow-up was 10.5 years . Ten patients died of their disease. No patient with a benign tumor h ad recurrence or metastasis, but all patients with high-grade malignan cy had died of disease within 3 years after diagnosis. Seventy-five pe rcent of proximal tumors were malignant. Extent of resection had no im pact on survival (p = 0.5). Conclusions. The best determinant of tumor behavior was histologic grade. Twenty-seven percent of patients had m alignant tumors, and 67% of these died of disease. Other significant p rognostic factors included a mitotic count greater than 5/10 high-powe r fields, size larger than 6 cm, aneuploidy, and higher S-phase fracti on (p < 0.01). Proximal lesions were more likely to be malignant, Exte nt of surgical treatment had no effect on survival.