Paraneoplastic Syndromes: Cancer's Dark Passenger

Paraneoplastic syndromes (PNS) are changes in bodily structure or function that are not directly caused by cancer itself; rather, they arise secondary to tumor production of small molecules (such as hormones, cytokines, or peptides), tumor depletion of small molecules, or the host immune response to the cancer. PNS may precede a diagnosis of cancer as the first sign of disease, and, when recurrent, are typically a harbinger of relapse. While many PNS resolve with successful treatment of the underlying cancer, some syndromes persist despite tumor response to therapy, and may cause significant ongoing patient morbidity.