Tumorlike conditions of the pleura.

Tumorlike conditions of the pleura are rare, but diagnosis is facilitated by recognizing certain imaging patterns and interpreting them in the clinical context. A tumorlike condition of the pleura is any nonneoplastic lesion of the pleura itself, or within the pleural space, that resembles a tumor. An approach to diagnosis of the tumorlike conditions of the pleura is provided, and these conditions are grouped into focal or diffuse conditions, with an emphasis on specific imaging features. Focal tumorlike conditions of the pleura include pleural plaque, thoracic splenosis, thoracic endometriosis causing catamenial pneumothorax, and pseudotumor caused by pleural effusion. Thoracic splenosis should be considered in a patient who has a healed left lower rib fracture, an absent spleen, and left lower pleural nodules. Thoracic endometriosis with catamenial pneumothorax should be considered in a woman of childbearing age who presents with right scapular pain and recurrent pneumothorax occurring at or around the onset of menses. Extrapleural hematoma is a nonpleural mimic of pleural tumor and shares some imaging features with focal tumorlike conditions of the pleura, despite residing in the extrapleural space. Diffuse tumorlike conditions of the pleura include diffuse pleural thickening and rare conditions such as Erdheim-Chester disease and diffuse pulmonary lymphangiomatosis. Erdheim-Chester disease should be considered when diffuse pleural thickening occurs with a perirenal soft-tissue halo or distal femoral sclerosis. Diffuse pulmonary lymphangiomatosis should be considered when findings include diffuse pleural thickening, interlobular septal and peribronchovascular interstitial thickening, and mediastinal fat infiltration limited to the thorax and when these findings persist despite diuretic therapy.