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Background
Developmentally, the presacral space is a complex compartment containing derivatives of numerous types of primordial germ cells. As a consequence, it contains a number of structures, such as vascular structures, neural elements, lymph nodes, fat, skeletal and smooth muscles, and other mesenchymal derivatives, which serve as the source of a wide variety of tumors. As previously reported in the medical literature, the incidence of presacral tumors ranges from 1.4 to 6.3 cases per year, and they are typically diagnosed in patients between 30 and 50 years of age. The incidence of pediatric presacral masses is even lower. The majority of presacral lesions are benign and congenital.

Educational Goals / Teaching Points
The primary objective of the current educational exhibit is to describe a method for evaluating presacral masses on imaging by paying close attention to imaging characteristics, thereby enabling the differential diagnosis of these masses to be refined. Describe in detail clinically significant characteristics that may influence biopsy or surgical approach and of which the radiologist must be aware. A literature review was conducted on the diagnosis and treatment of presacral masses, with a focus on specific characteristics that may aid in refining the differential diagnosis of these masses.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The presacral space is an extraperitoneal potential space between the sacrum and the upper two-thirds of the rectum. The anterior retrorectal and posterior presacral spaces can be subdivided from the retrorectal space by the presacral fascia. In children, the presacral region can be affected by a variety of masses. The origin of a presacral mass may be congenital, developmental, or inflammatory. The mass can have neural, vascular, lymphatic, or mesenchymal origins and can be either primary (as in focal disease) or systemic (as in multifocal disease). In the evaluation of presacral lesions, CT and MRI scans are now utilized in a complementary fashion. A CT scan can be used to determine whether a lesion is solid or cystic, to evaluate cortical bone destruction, and to determine whether adjacent viscera are involved. MRI assists in determining the planes of resection, spatial relationship to adjacent structures, associated cord abnormalities, and bone marrow involvement extent.

Conclusion
As the clinical manifestations of presacral masses are frequently nonspecific, imaging plays a crucial role in their detection and differentiation. Imaging information is also indispensable for administration, particularly surgical planning. For these reasons, it is crucial that radiologists understand the anatomy of the presacral region and the imaging characteristics of the numerous lesions that can occur in this region in children. For accurate interpretation of findings, radiologists must also be familiar with the specific benefits and limitations of each imaging modality used to evaluate this class of abnormalities.