Primary Retroperitoneal Neoplasms: CT and MR Imaging Findings with Anatomic and Pathologic Diagnostic Clues

Abstract

Primary retroperitoneal neoplasms are a rare but diverse group of benign and malignant tumors that arise within the retroperitoneal space but outside the major organs in this space. Although computed tomography and magnetic resonance imaging can demonstrate important characteristics of these tumors, diagnosis is often challenging for radiologists. Diagnostic challenges include precise localization of the lesion, determination of the extent of invasion, and characterization of the specific pathologic type. The first step is to determine whether the tumor is located within the retroperitoneal space. Displacement of normal anatomic structures of the retroperitoneum is helpful in this regard. For tumors that are located within the retroperitoneum, the next step is to identify the organ of origin. Specific signs, including the "beak sign," the "embedded organ sign," and the "phantom (invisible) organ sign," are useful for this purpose. When there is no definite sign that suggests the organ of origin, the diagnosis of a primary retroperitoneal tumor becomes likely. Awareness of specific patterns of spread, specific tumor components, and tumor vascularity help in further narrowing the differential diagnosis. Attention to these diagnostic clues is essential in making an accurate radiologic diagnosis of primary retroperitoneal tumors and in obtaining clinically significant information.

Detection and management of retroperitoneal cystic lesions: A case report and review of the literature

“…Upon CT scan, paragangliomas are well-circumscribed masses, with contrast enhancement due to increased vascularization. Upon MRI, paragangliomas are hypointense or isointense to the liver parenchyma on T1-weighted images and markedly hyperintense on T2-weighted images (76,77). In certain cases, scintigraphy with iodine-123-labeled metaiodobenzylguanicintigraphy with iodine-123-labeled metaiodobenzylguanidine can facilitate the diagnosis due to its superior specificity compared with CT and MRI imaging (78).…”

Pitfalls in Imaging of Female Pelvic Masses

“…The ''beak'' sign occurs when a mass deforms the edge of its organ of origin into a beak shape [19,20] (Fig. 11).…”

“…''Prominent feeding artery'' sign is seen when an artery is enlarged because of tumour vascular supply [19,20]. Anatomical recognition of the dilated artery may allow the radiologist to diagnose the origin of the tumour (Fig.…”

Malignant fibrous histiocytoma in a patient presenting with urinary system symptoms

“…Large dimensions at the time of diagnosis, absence of renal vein or vena cava involvement, characteristic signs of fibrous components and necrotic/hemorrhagic or calcific components raise suspicion for MFH. 9 The prognosis of MFH is generally poor. Determinant prognostic factors are subgroup type and location of the tumor, as well as presence of metastases or paraneoplastic syndrome.…”

“…Prognosis is better in tumors located in extremities compared to retroperitoneal or deeply located tumors. 9,10 Primary treatment of MFH is surgical excision of the mass. Radiotherapy plays an important role in the postsurgical treatment; however, the efficacy of chemotherapy is controversial.…”