Primary retroperitoneal soft tissue sarcoma: Imaging appearances, pitfalls and diagnostic algorithm

Abstract

Although retroperitoneal sarcomas are rare tumours, they can be encountered by a wide variety of clinicians as they can be incidental findings on imaging or present with non specific symptoms and signs. Surgical resection can offer hope of cure and patient outcomes are improved when patients are managed in high-volume specialist centers. Failure to recognize retroperitoneal sarcomas on imaging can lead to inappropriate management in inexperienced centers. Therefore it is critical that a diagnosis of retroperitoneal sarcoma should be considered in the differential diagnosis of a retroperitoneal mass with prompt referral to a soft tissue sarcoma unit. In particular, the most common retroperitoneal sarcoma subtypes, liposarcoma and leiomyosarcoma, have characteristic imaging appearances which are discussed. This review therefore aims to set the context and guide clinicians through a diagnostic pathway for retroperitoneal masses in adults which arise extrinsic to the solid abdominal viscera.

Imaging in retroperitoneal soft tissue sarcoma

“…Sometimes the fat containing mass originates from the kidney or adrenal leading to a diagnosis of renal angiomyolipoma (AML) or adrenal myelolipoma (ML) respectively (Figure ). The presence of renal cortical defects and prominent vessels strengthens diagnosis of the AML and adrenal ML tend to be more well defined than RP liposarcoma, with a frosted glass aspect which is related to the bone marrow inside the fat. If the lipomatous mass is not clearly arising from the solid abdominal viscera the diagnosis of retroperitoneal liposarcoma should be considered and referral to a soft tissue sarcoma unit made where percutaneous biopsy will be performed.…”

“…Other less common subtypes occurring in the retroperitoneum include solitary fibrous tumor (SFT), undifferentiated pleomorphic sarcoma (UPS), malignant peripheral nerve sheath tumor, synovial sarcoma, and extraosseous Ewing's sarcoma. However, because soft tissue sarcoma accounts for only a third of retroperitoneal tumors, other diagnoses must be considered …”

Mixed extragonadal germ cell tumour of the prostate

“…Positive serum markers may suggest a diagnosis of germ cell tumours and therefore should always be evaluated, especially if there is no evidence of fat on CT scan. The majority (70%) of retroperitoneal sarcomas are liposarcomas and therefore interrogating imaging of an indeterminate retroperitoneal mass should begin with a purposeful search for the presence of abnormal macroscopic fat 12. An accurate diagnosis after TURP would have prevented chemotherapy with doxorubicin and possibly even radical cystoprostatectomy.…”

Major vascular resections in retroperitoneal sarcoma

“…The standard method for the staging of RPS is a contrast tomography (CT) scan of the chest/abdomen/pelvis with IV contrast or MRI angiography to characterize the local extent of the tumor, as well as a CT of the chest to identify pulmonary metastasis . A large mass centered within major vessels evokes a rather primary sarcoma arising from the major vessels, the large majority of which are leiomyosarcomas (Figures and ).…”