Imaging features and metastatic pattern of non-IVC retroperitoneal leiomyosarcomas: are they different from IVC leiomyosarcomas?

PURPOSE: The purposes of this study were to describe the imaging features and metastatic pattern of non-inferior vena cava (IVC) retroperitoneal leiomyosarcomas (non-IVC LMS) and to compare them with those of IVC leiomyosarcomas (IVC LMS) to assess any differences between the 2 groups. MATERIALS AND METHODS: In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant retrospective study, all 56 patients with pathologically confirmed primary retroperitoneal leiomyosarcoma (34 non-IVC LMS and 22 IVC LMS) seen at our tertiary cancer center during a 10-year period were included. All available imaging of primary tumor (18 non-IVC LMS and 19 IVC LMS) and follow-up imaging studies (on all 56 patients) were reviewed in consensus by 2 fellowship-trained oncoradiologists. Imaging features and metastatic spread of non-IVC LMS were described and compared with those of IVC LMS. Continuous variables were compared using the Student t test, binary variables with the Fisher exact test, and survival using the log-rank test. RESULTS: Non-inferior vena cava retroperitoneal leiomyosarcomas had a mean size of 11.3 cm (range, 3.7-27 cm) and most commonly occurred in the perirenal space (16/18). Primary tumors were hyperattenuating to muscle (11/18) and showed heterogeneous enhancement (17/18). Lungs (22/34), peritoneum (18/34), and liver (18/34) were the most common metastatic sites. There was no significant difference between the imaging features and metastatic pattern of non-IVC and IVC LMS. Although non-IVC LMS presented at a more advanced stage (P < 0.002), there was statistically non-significant trend toward better median survival of non-IVC LMS (P = 0.07). CONCLUSIONS: Non-inferior vena cava retroperitoneal leiomyosarcomas are large heterogeneous tumors arising in the perirenal space and frequently metastasize to lungs, peritoneum, and liver. From a radiologist's perspective, non-IVC LMS behave similar to IVC-LMS.