Practical Imaging Approach to Complex Pelvic Lesions: The Onco-surgeons' Perspective

Abstract The pelvis is an anatomically intricate region comprising multiple organ systems, complex fascial planes, and densely packed neurovascular structures. Tumors arising in this region—such as soft tissue neoplasms, sarcomas, and metastatic lesions—pose significant diagnostic and surgical challenges due to their deep location, large size at presentation, and proximity to critical anatomical structures. Compared with appendicular skeletal tumors, pelvic neoplasms demand meticulous preoperative planning to achieve oncologic clearance while preserving function. A compartment-based anatomical framework, grounded in embryological development and surgical fascial planes, offers a systematic method for tumor localization, staging, and treatment planning. Although widely used in surgical oncology, this compartmental approach is underutilized in radiologic practice. Advances in high-resolution magnetic resonance imaging (MRI) and hybrid imaging modalities such as positron emission tomography-computed tomography (PET-CT) now enable radiologists to apply compartmental principles effectively. MRI's superior soft-tissue contrast delineates fascial boundaries and tumor infiltration with precision, while PET-CT provides essential metabolic information for nodal staging and treatment monitoring. This case-based review explores the imaging evaluation of pelvic tumors across anterior, middle, and posterior compartments, emphasizing the relevance of fascial anatomy—including the mesorectal, presacral, Denonvilliers', and rectovaginal fasciae—in guiding surgical planning. Specific attention is given to the radiologic depiction of these fascial planes, their embryological significance, and their impact on operative strategies such as nerve-sparing techniques and compartmental resections. Understanding pelvic compartmental anatomy through imaging enhances interdisciplinary communication, aids in selecting optimal surgical planes, and ultimately improves oncologic and functional outcomes in patients with complex pelvic malignancies, as demonstrated through selected case illustrations.