Leiomyosarcoma is a rare malignant tumour originating from the smooth muscular tissue in any part of the organism, including retroperitoneum where it is particularly aggressive. It is nearly always characterized by a silent development causing diagnostic delay. The results of the primary therapy, which is always surgical, are limited because of the tumoral mass extension and the high local aggressiveness. The Authors present a clinical case which was under their observation and seize the opportunity of making a revision of the literature about it.