Detailed clinical course of a patient with rapidly progressing sarcomatoid pleural mesothelioma without p16 deletion with systemic haematogenous metastasis to soft tissues.

Sarcomatoid mesothelioma is difficult to differentiate from other mesotheliomas. Here, we describe the case of a man in his early 80s with sarcomatoid mesothelioma and a history of asbestos exposure. He initially presented with right-sided chest pain and was examined. Right-sided pleural effusion was detected; therefore, he was hospitalised. Based on the observed pleural effusion and biopsy result, the presence of a malignant tumour was excluded; hence, he was diagnosed with benign asbestos pleurisy. He subsequently developed left-sided pleural effusion, masses and lung nodules, and died 9.5 months after the initial examination. A definitive diagnosis of sarcomatoid mesothelioma with rapid systemic progression was established after detailed investigations using autopsy specimens. This rare case of mesothelioma-without p16 deletion (detected using fluorescence in situ hybridisation)-presented differently from the usual sarcomatoid mesothelioma.