EN
Inferior vena cava leiomyosarcoma is a malignant neoplasm rarely diagnosed. The study presented two cases of inferior vena cava leiomyosarcomas subject to treatment at the Department of Oncology, Center of Oncology in Warsaw. The first patient underwent surgery after a two-year thorough gastroenterological diagnostic process, being suspected of pancreatic cancer. Proper diagnosis was established intraoperatively, the tumor was completely excised. After ten months the patient was subject to chemotherapy, due to the presence of distant metastatic lesions. Chemotherapy was stopped after 24 months, due to disease progression. The patient died six months, thereafter. The second patient underwent surgery after a short diagnostic process, being suspected of an adrenal gland tumor. Proper diagnosis was established intraoperatively, and the tumor was completely excised. The patient remained under close oncological control. Three years after the procedure disease recurrence was not observed. Retroperitoneal space tumors pose a significant clinical problem. Rapid diagnosis and proper therapeutic decisions often determine the future of such patients. The five-year survival rate of patients subject to radical surgical treatment, due to inferior vena cava leiomyosarcomasa ranges between 33 and 55%.