Paraendocrine syndromes of cancer

Understanding of the humoral manifestations of cancer has steadily increased over recent years. The endocrine syndromes, where they are understood, appear to be caused by increased production by the cancer of protein hormones, protein hormone precursors, or protein hormone-like substances. These proteins are commonly produced also by nonneoplastic, nonendocrine cells, and presumably represent paracrine or autocrine substances. Many of the neurologic syndromes, and possibly a wide range of other paraneoplastic syndromes, appear to be caused by tumor immunogen stimulation of antibodies that cross-react not only with the specific tumor antigen but also with antigens from host tissues. Antibody-mediated cell injury leads to the specific symptoms, determined by the tissue injured. Some of the hematologic paraneoplastic syndromes (e.g., aplastic anemia, red cell aplasia) may also be produced by immune mechanisms. Finally, at least one syndrome, multifocal leukoencephalopathy, is caused by a viral infection. Presumably the host with cancer is more susceptible to such infections. The pathogenesis of many syndromes caused by cancers remains unclear. The amino acid structure of the hormones produced by cancers has not been determined for any of the syndromes. The function of these protein hormones produced by normal, nonendocrine tissues is unknown.