Uterine leiomyosarcomas (LMS) are difficult to distinguish from benign leiomyomas without surgery. In this study we performed transcervical needle biopsy on 475 patients, 8 LMS patients and 467 patients with non-sarcomas (non-LMS) in a high-risk group for LMS, and evaluated whether examinations performed with Ki-67 and CD34 immunohistochemical analyses in addition to the standard hematoxylin-eosin (H&E)-stained sections would improve preoperative diagnostic precision of the uterine smooth muscle tumors. Histopathologic analysis included three factors: degree of cytologic atypia, mitotic index and coagulative tumor cell necrosis (CTCN). We also evaluated cell proliferation with Ki-67 expression. In cases of suspected CTCN, we examined CD34 expression and counted positive blood vessels in the necrotic area. Three of the 8 LMS cases satisfied the diagnostic criteria of LMS by histopathologic evaluation with H&E-stained sections. We made a score list based on these analyses; scores for LMS specimens ranged from 6-14 points; non-LMS specimens scored 0-2 points. At the cut-off score of 6 points, the positive predictive value to distinguish LMS from non-LMS was 100%, showing that this scoring system, is a useful method for preoperative differentiation between LMS and non-LMS tumors.