Trastuzumab-emtansine induced pleural and pericardial effusions.

To our knowledge, this is the first case in the literature of bilateral pleural and pericardial effusions in a patient treated with T-DM1. The successful initiation of treatment with trastuzumab following withdrawal of T-DM1 suggests that emtansine played a role in the development of bilateral pleural and pericardial effusions. We hypothesize that the patient's condition was a result of a local inflammatory reaction to emtansine by direct toxicity.