**Note 1:** Physician statement of pleural effusion can be used to code this data item when no other information is available.
**Note 2:** One of the most common symptoms of mesothelioma is a pleural effusion, or an accumulation of fluid between the parietal pleura (the pleura covering the chest wall and diaphragm) and the visceral pleura (the pleura covering the lungs). Record the absence or presence of pleural effusion and specifically, if present, whether the pleural effusion is non-malignant, malignant, atypical or NOS.
**Note 3:** If imaging indicates a pleural effusion but pleural fluid cytology is described as negative for malignant cells, assign code 1.
**Note 4:** If pleural fluid cytology is described as suspicious/suspicious for mesothelioma, assign code 2.