By means of the present dissertation, uterine leiomyosarcomas (LMS) were extensively characterized to serve as reference material for regular leiomyomas (LM) for the calculation of a preoperative LMS risk score based on a larger patient collective. In order to allow a comparative evaluation with LM, it was necessary to integrate the relevant criteria into a schema that was used simultaneously in the LM analyzes of the other working groups. The results obtained were used in the headquarters of the DKSM for the calculation of the LMS risk score by comparison with 670 prospectively analyzed LMS from 2 further graduations. The score has been published in the meantime.