[Mesenchymoma--diagnostic dilemmas]

This is a case report on retroperitoneal localization of a tumor formed of mixed-chondromatous tissue, bone tissue, fatty tissue and connective tissue together with angiomatous areas with blood vessels having unevenly thickened walls, being histopathologically diagnosed as a mesenchymoma. Apart from presenting the tumor, this paper deals with diagnostic dilemmas in cases of mixed tumors of mesenchymal origin because of numerous disagreements in literature data on morphologic characteristics, biological behavior and diverse nomenclature.