Diffuse Malignant Mesothelioma
Frozen section of pleural tissue is performed during surgery to confirm that diagnostic tissue has been obtained for permanent section examination and to decide on intraoperative therapy. Benign reactive/inflammatory conditions (infections, plaques, pleuritis of various etiologies), benign neoplasms, primary pleural malignancies, and metastatic cancers may produce overlapping radiologic, clinical, or gross findings. These diverse pleural diseases (1) may cause pleural thickening, nodules or masses observed on imaging studies or grossly by the surgeon, (2) are often accompanied by pleural effusions, and (3) may be asymptomatic or cause difficulty in breathing, chest pain, or other thoracic symptoms, regardless of the etiology. The suspected diagnosis based on clinical context and current imaging modalities often proves correct. However, even the most recent advances in noninvasive diagnosis have limitations. For example, a few cases of malignancy will be negative on positron emission tomography (PET) using 18-fluorodeoxyglucose (FDG), and some benign reactive/inflammatory conditions will be positive. Even when a diagnosis of cancer is correctly rendered on a clinical and radiologic basis, histologic examination may be necessary to determine the type of malignancy involving the pleura. Therefore, even with modern imaging techniques, t he definitive diagnosis of a pleural abnormality often requires tissue samples.