Malignant causes of fever of unknown origin.

The presence of fever in malignancy usually indicates infection, though transfusion, thrombosis and drugs are also culprits. However, particularly in some tumour types, fever can also be a paraneoplastic syndrome, caused by the malignancy itself. This can be a difficult diagnosis to establish and presents a therapeutic challenge to the physician when the underlying malignancy is not easily treated. © Royal College of Physicians 2015. All rights reserved.