Presentation
Right, posterior thoracic non-pleuritic pain, progressive dyspnea, with weight loss. There is no significant past medical history.
Patient Data
There are bibasal pleural reactions with compressive atelectasis, the right is worse than the left.
There is a normal CTR and there are no features to suggest biventricular cardiac decompensation.
Right, basal consolidation cannot be excluded, however, there are no air bronchograms.
There are no suspicious nodules or masses on the chest X-ray given the weight loss.
There is circumferential mass-like pleural thickening encasing the right lung. This extends from apex to base and measures soft tissue density at 30-40 HU on pre-contrast and 60-70 HU on post-contrast imaging. At this stage, there is no right hemithoracic volume loss with a central trachea and cardiomediastinum. There is no trans diaphragmatic extension, no extrathoracic invasion, no rib or thoracic vertebral involvement, and there are no suspicious retrosternal, hilar or mediastinal lymph nodes. The mass is inseparable from the right pericardium however there is no transpericardial involvement and there is no pericardial effusion. The left basal pleural reaction on chest X-ray is confirmed to represent a small simple pleural effusion, with no nodularity, and no abnormal enhancement. There are bi-basal interstitial changes, right basal compressive atelectasis and non-specific right basal ground glass attenuation. There are no suspicious parenchymal nodules bilaterally. Importantly there are no calcified pleural plaques, and no features to suggest asbestos exposure or asbestosis.
The chest X-ray demonstrates significant progression of the right pleural mass with significant right lung encasement, given the known diagnosis and previous CT imaging findings. There is a persistent left basal pleural reaction, minimally progressive in comparison to the initial chest X-ray. There is a relatively central tracheomediastinum.
Immunohistochemistry:
AE1/3- positive
CK7- positive
CK20- negative
Calretinin- positive
Napsin A- negative
CDX2- negative
The Calretinin positivity is consistent with mesothelial origin and the histopathological features suggest an epithelioid mesothelioma.
Case Discussion
A histopathologically confirmed epithelioid mesothelioma on pleural biopsy. Based on the Initial CT appearance it was staged at least a T2N0M0. The left basal pleural reaction is worrying for contralateral pleural involvement even though the CT confirmed a small simple pleural effusion. Should this be the case, the mesothelioma would be a stage T4.
A differential diagnosis of pleural carcinomatosis in a setting of an unknown primary malignancy (especially a gastrointestinal adenocarcinoma) cannot be excluded from the initial imaging findings and was offered as a reasonable differential diagnosis in the absence of any features to suggest asbestos exposure.
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