Intrathoracic splenosis: evaluation by superparamagnetic iron oxide-enhanced magnetic resonance imaging and radionuclide scintigraphy.

Splenosis represents the heterotopic autotransplantation of splenic tissue after either splenic trauma or surgery. Intrathoracic splenosis is a rare condition resulting from concomitant rupture of the spleen and the left hemidiaphragm. We report a case of splenosis in a 41-year-old male patient who had experienced severe thoracoabdominal injury including rupture of the spleen and left hemidiaphragm and post-traumatic splenectomy 20 years previously. Abnormal opacities in the cardiac region were noted on a chest radiograph at an annual checkup. Computed tomography (CT) of the chest demonstrated multiple, well-circumscribed pleura-based nodules at the posterior base of the left hemithorax and the left subdiaphragmatic area. On magnetic resonance imaging (MRI), the lesions were hypointense on T1-weighted images and hyperintense on T2-weighted images. After administration of superparamagnetic iron oxide (SPIO), the lesions showed decreased signal intensity but remained slightly hyperintense relative to liver parenchyma on T2-weighted images. (99m)Tc-labeled Sn colloid scintigraphy revealed multiple areas of increased activity consistent with the lesions on the CT and MRI scans. In addition to the history of splenic trauma and left hemothorax, SPIO-enhanced MRI and radionuclide scintigraphy, which can demonstrate phagocytic ability in the ectopic splenic tissue, were useful for confirming the diagnosis.