Clinicopathological Study of Gastric Smooth Muscle Tumors

We investigated the tumor malignancy in 37 patients with tumors of the gastric smooth muscle (14 with leiomyoma, 20 with leiomyosaicoma, and 3 with leiomyoblastoma) encountered during the past 19 years in our department. These patients were devided into 3 groups: Group A, consisting of 14 patients with leiomyoma; Group B, 13 patients with leiomyosarcoma or leiomyoblastoma who had no recurrence; and Group C, 6 patients with leiomyosarcoma or leiomyoblastoma who were treated by non-curative resection or had recurrence. Comparison of the tumor diameter, mitotic figures, cellularity, the area and morphology of the nucleus, and tumor morphology of the nucleus, and tumor fiber bundle formation among these groups suggested that the tumor diameter, mitotic figure, morphology of the nucleus, and tumor fiber bundle formation are important factors associated with tumor malignancy. Patients with tumors 5 cm or less in diameter showed a benign course while those with tumors more than 10 cm in diameter had a poor outcome. The outcome was also poor in patients showing mitotic figures exceeding a mean value in 10 visual fields (×400) of 3.0/HPF. The morphology of the nucleus was associated with tumor fiber bundle formation. The outcome was favorable in patients with a spindle shaped uncleus and obvious tumor fiber bundle formation but poor in those with a round nucleus and unclear fiber bundle formation.