Uncommon Nonneoplastic Lesions of the Pleura
There are several nonneoplastic lesions of the pleura that, although uncommon, should be differentiated from pleural neoplasms. Sclerosing mediastinitis presents as an extensive dense fibrous tissue in the mediastinum that compresses, entraps, and invades chest structures, including pleura, bronchi, and lungs, often grossly mimicking invasive neoplasm (Fig. 5.1). Patients may be of any age, with the greatest frequency in patients in their 40s to 60s. Patients may experience compression of the superior vena cava (superior vena cava syndrome), bronchi, pulmonary hilum, and/or esophagus. Presenting symptoms include cough, dyspnea, hemoptysis, and chest pain. There may be a clinical suspicion of cancer involving the pleura and other structures of the chest including diffuse malignant mesothelioma and lung cancer in the differential diagnosis. The diagnosis typically requires a surgical biopsy, often with frozen section, and the pathologist may feel pressure to diagnose malignancy at the time of frozen section because of the clinical presentation. However, the frozen section will typically show thick ropey collagen with or without a mixed inflammatory infiltrate of lymphocytes, plasma cells, and eosinophils. There is a frequent association with infections, particularly Histoplasma and tuberculosis, and so special stains should be obtained on the permanent sections.