Malignant pleural mesothelioma presenting with remitting–relapsing pleural effusions: report of two cases

Pleural effusions are common and are associated with malignancy in one sixth of cases. Malignant pleural effusion (MPE) is typically persistent and progressive, prompting further investigations if the initial tests are not diagnostic. A spontaneously remitting effusion is commonly presumed to be benign, and further investigations may not be performed. We present two cases in which the presenting pleural effusion spontaneously resolved but recurred (in one case, multiple times), leading to further investigations that revealed an underlying malignant pleural epithelioid mesothelioma. These cases demonstrate the need for clinicians to be aware that remitting effusions can occur in the context of pleural malignancy and should be kept under observation, with a low threshold for further investigation if relapse occurs.