Indeterminate Retroperitoneal Masses

Abstract Retroperitoneal (RP) masses represent a wide variety of pathologies. They can grow to substantial size before presenting symptoms that lead imaging work-up. are also often detected incidentally due increased use cross-sectional imaging. Contrast-enhanced CT is the modality choice, yet MRI clarify involvement muscle, bone, or neural foramina. 18 F FDG PET/CT not routinely indicated, however, for lesions which inaccessible percutaneous biopsy it differentiate between intermediate/high-grade and low grade/benign lesions. This chapter aims describe most common indeterminate RP highlight features help in differential diagnosis.