Widespread pulmonary invasion by malignant pleural mesothelioma: an important diagnostic consideration.

We report a rare case of early and extensive pulmonary invasion of malignant pleural mesothelioma (MPM) in a 70-year-old woman. She first presented with a hydropneumothorax and subsequent workup, including video-assisted thoracoscopy (VAT), confirmed MPM. After VAT, she developed dyspnoea, cough, and widespread pulmonary infiltrates of uncertain aetiology. These infiltrates progressed over the following months, failed to respond to antibiotics, and were strongly fluorodeoxyglucose (FDG)-avid on positron emission tomography (PET). Bronchoalveolar lavage (BAL) yielded extremely viscous fluid containing mesothelioma cells. These cells were also found in the sputum when nebulized deoxyribonuclease (DNase) was trialled to enhance clearance of the pulmonary fluid. The patient deteriorated rapidly with progressive mediastinal and contralateral MPM involvement and died one month later. This case highlights the importance of including tumour invasion as a differential diagnosis of non-resolving pulmonary infiltrates in patients with MPM.