Primary pleural tumor is mainly localized fibrous tumor and diffuse pleural mesothelioma.
Clinical presentation and pathology
Localized fibrous tumor may have no clinical symptoms and is often discovered accidentally. Diffuse pleural mesothelioma may be manifested by thoracodynia, often severe pain, accompanied by cough and dyspnea, and some patients may have pulmonary hypertrophic osteoarthropathy.
Localized fibrous tumor originates from pleural fibroblasts, mostly benign, but about 1/3 are malignant. Diffuse pleural mesothelioma is malignant, and may be related to exposure to asbestos in some patients. The lesion can originate from the visceral or parietal pleura, mostly the former.
Imaging manifestations
X-ray
Sometimes, only pleural effusion is seen on the chest film. When the localized lesion is large, a nodule or mass protruding into the lung field can be seen. The bottom of the tumor is generally wide and flat, and is adhered to the inner wall of the chest.
CT
On plain CT, localized fibrous tumor is mainly in the parietal pleura, often subrounded, with homogeneous density and smooth and sharp edges, and can intersect with the pleura at an acute or obtuse angle; few are pedunculated. Contrast-enhanced CT shows homogeneous enhancement.
Diffuse pleural mesothelioma is manifested by extensive nodular or irregular thickening of the pleura, mostly the lower part of the pleural cavity, involves the mediastinal pleura and interlobar pleura, and is often accompanied by pleural effusion. Some patients have enlarged mediastinal lymph nodes and vertebral or rib destruction.
Figure 1 Diffuse pleural mesothelioma
Contrast-enhanced CT mediastinal window shows diffuse and irregular thickening of the right pleura accompanied by a soft tissue mass (↗) on the mediastinal side of the pleura, with homogeneous density, clear edges, and slight enhancement.
MRI
Localized fibrous tumor is mostly regular in shape and shows homogeneous signals. Diffuse pleural mesothelioma is irregularly massive or irregularly serrated, and is slightly hyperintense on T1WI and hyperintense on T2WI. Bloody pleural effusion is hyperintense on both T1WI and T2WI.
Diagnosis and differential diagnosis
Localized fibrous tumor shows nodular opacity with smooth edges, without apparent changes in dynamic observation, and is clinically asymptomatic, so it is not difficult to diagnose. When the tumor is large, it needs to be differentiated from pleural sarcoma or other extrapulmonary lesions.
Diffuse pleural mesothelioma is often manifested by extensive, irregular, significant, nodular thickening of the pleura, accompanied by pleural effusion. On the basis of severe clinical symptoms and rapid progression, it can often be diagnosed, but it still needs to be differentiated from metastatic tumors.