Abnormal opacities detected at chest radiography must be localized as parenchymal or extraparenchymal to facilitate differential diagnosis. Extraparenchymal opacities may arise from the chest wall soft tissues, osseous structures, or pleura. Regarding the latter, pleural effusion and fibrothorax are commonly recognized patterns of pleural disease encountered at thoracic imaging. Less commonly, nodules or masses arising from the pleura may be seen, and usually this imaging pattern reflects the presence of pleural malignancy. However, there are rare conditions that may affect the pleura and simulate malignant pleural disease, particularly thoracic splenosis. Splenosis represents autotransplantation of functional splenic tissue into ectopic sites, most frequently within the abdomen, and rarel...