Beyond the surface: A comprehensive radiological review of primary retroperitoneal neoplasms.

Primary retroperitoneal neoplasms (PRNs) are a complex and diverse group of tumors arising in the retroperitoneal space, excluding those from retroperitoneal organs. These masses present significant diagnostic challenges due to their heterogeneous nature. PRNs primarily include sarcomas, neurogenic tumors, extragonadal germ cell tumors, and lymphomas, with the majority being malignant. This necessitates thorough evaluation by radiologists to assess resectability and the need for biopsy. Liposarcomas, the most common primary retroperitoneal sarcomas, and leiomyosarcomas, known for potential vessel involvement, exhibit distinct imaging patterns aiding differentiation. Neurogenic tumors, originating from nerve sheath, ganglionic, or paraganglionic cells, often appear in younger patients and have characteristic imaging features. Primary retroperitoneal extragonadal germ cell tumors are rare and are believed to originate from primordial germ cells that do not successfully migrate during embryonic development. Lymphomas are generally homogeneous on cross-sectional imaging; however, non-Hodgkin lymphomas can sometimes appear heterogeneous, complicating differentiation from other non-lipomatous retroperitoneal masses. Additionally, conditions like retroperitoneal fibrosis and Erdheim-Chester disease can mimic PRNs, complicating diagnosis and management. This review aims to provide radiologists with essential diagnostic points for identifying PRNs, emphasizing the importance of precise imaging interpretation. Understanding these distinctions is vital for guiding clinical management and optimizing patient outcomes.