Retroperitoneal dermoid cysts are rare entities, accounting for only 1-11% of primary retroperitoneal tumors. These lesions are often asymptomatic or present with non-specific abdominal symptoms. A 35-year-old Middle Eastern female presented with fever, dysuria, right flank pain, and gait disturbance following intrauterine device insertion. Ultrasound incidentally revealed a periadrenal lesion. Non-contrast CT showed a 7.3 × 3.6 cm cystic lesion within the right psoas muscle abutting the adrenal gland. Contrast-enhanced MRI demonstrated a 7.8 × 4.4 × 3.4 cm mass extending from T12-L1 to L2-L3, partially embedded within the psoas and displacing the adrenal superiorly. A predominantly enhancing solid nodule (1.5 × 1.8 cm) at the inferior aspect raised concern for malignant transformation. Biochemical workup (cortisol suppression test, 24-hour urinary metanephrines) excluded functional pathology. Imaging revealed no additional lesions, lymphadenopathy, or metastases. Following tumor board discussion, surgical excision via open retroperitoneal approach was performed. Histopathology confirmed mature cystic teratoma with a benign mural nodule (dermoid plug). The mass was completely excised with clear surgical margins. Postoperative recovery was uneventful with complete resolution of presenting symptoms. This case highlights the diagnostic challenge of periadrenal dermoid cysts with psoas muscle involvement presenting with gait disturbance. Mural nodules can mimic malignancy on imaging, necessitating histopathological confirmation for definitive diagnosis. We provide a systematic comparison of differential diagnoses including radiological, biochemical, and pathological features to aid clinicians encountering similar cases. • A rare symptomatic retroperitoneal dermoid cyst with direct psoas muscle involvement is reported. • The case highlights diagnostic challenges of periadrenal masses with atypical imaging features. • Preoperative endocrine workup is crucial to safely exclude functional adrenal tumors. • An enhancing mural nodule mimicked malignant transformation, requiring histologic confirmation. • A comprehensive comparative table provides a practical diagnostic framework for retroperitoneal tumors.
Khalife et al. (Sun,) studied this question.