Paraneoplastic syndromes in cancers of unknown primary: An unknown field for oncologists

Paraneoplastic syndromes are signs or symptoms that result from tissue damage at locations remote from tumour sites. Paraneoplastic syndromes associated with cancer of unknown primary (CUP) are not well recognized as they are rarely reported. These syndromes can impair various organ functions and include endocrine, neurologic, dermatologic, rheumatologic, hematologic and several other system alterations. To our knowledge, the association between the histological CUP type and the paraneoplastic syndrome has never been assessed. In some instances, paraneoplastic syndromes can become the major clinical problems determining survival. However, they can also herald earlier the occurrence of CUP in patients with asymptomatic tumors. In this article, we review the available literature of CUP patients presenting paraneoplastic syndromes by trying to collect all available published cases during the last three decades. One additional goal of this article is to make practicing oncologists aware of the coexistence of paraneoplastic syndromes in patients with CUP.