Paraneoplastic syndromes

As the lengthy but nonetheless incomplete review suggests, paraneoplastic syndromes are protean in their manifestations and, for the most part, poorly understood. Indeed, some of the more common abnormalities in cancer patients that might be considered paraneoplastic--such as anorexia-cachexia syndrome or unexplained fever--have not been discussed because they are so poorly understood. Most of the syndromes reviewed are either clearly paraneoplastic or strongly associated with cancer. Their clinical importance does not lie in the number of patients affected; it is a small minority. Instead, the syndromes may occasionally be helpful in the diagnosis of cancer or in monitoring response to cancer therapy. They may also be confused with the effects of metastatic disease. In some patients, amelioration of the syndromes can reverse the patient's dominant symptoms and thus provide significant clinical palliation. In a more general context, studies of etiologic mechanisms in paraneoplastic syndromes may offer insights into a variety of unexplained abnormalities in cancer patients. The best-understood syndromes result from tumor production of biologically active substances or, to a lesser extent, from autoimmune phenomena. These would appear to be probable mechanisms in many recognized paraneoplastic syndromes of uncertain etiology and perhaps in some heretofore unrecognized paraneoplastic syndromes. Finally, paraneoplastic syndromes could also hold clues to the neoplastic process. Better understanding of the ways in which tumors regulate remote effects--such as release of TGFs--may ultimately enhance our knowledge of tumor growth itself.