Epithelioid gastric stromal tumors (leiomyoblastomas): a study of fifty-five cases.

Abstract

Epithelioid gastric stromal tumors form a distinct histologic subset of gastric tumors whose malignant potential and prognosis are controversial. Fifty-five patients with epithelioid gastric stromal tumors accounted for 11.5% of patients undergoing definitive operations for gastric stromal tumors from 1960 to 1986. Medical records and pathology slides were reviewed, and immunohistochemical staining and flow cytometry were performed. The Kaplan-Meier method was used to estimate survival. Survival curves were compared with log-rank tests and Cox proportional hazards model. 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 had recurrence of metastasis, but all patients with high-grade malignancy had died of disease within 3 years after diagnosis. Seventy-five percent of proximal tumors were malignant. Extent of resection had no impact on survival (p = 0.5). The best determinant of tumor behavior was histologic grade. Twenty-seven percent of patients had malignant tumors, and 67% of these died of disease. Other significant prognostic factors included a mitotic count greater than 5/10 high-power fields, size larger than 6 cm, aneuploidy, and higher S-phase fraction (p < 0.01). Proximal lesions were more likely to be malignant. Extent of surgical treatment had no effect on survival.