RESUMO
BACKGROUND: This case study details an ancient retroperitoneal schwannoma found incidentally on sonography and examines the rarity and characteristics of these tumors, as well as the role of sonography in diagnosis. DISCUSSION: Schwannomas-tumors that arise from a nerve sheath-predominantly are found on the flexor surfaces of the extremities, as well as the trunk, head, and neck. Retroperitoneal schwannomas are larger than other schwannomas and characterized by degenerative features. Schwannomas with degenerative changes are called ancient schwannomas; they are slow growing and benign with little malignant transformation. CONCLUSION: Assessing, diagnosing, and treating retroperitoneal schwannomas requires a blend of diagnostic imaging techniques. In this case study, sonography was a valuable adjunct modality used to locate the mass, and computed tomography was used to guide fine-needle aspiration and core biopsy. The mass was excised surgically, which is the preferred treatment.