Paraneoplastic syndromes are neoplasm-associated changes in body structure or function that are not directly caused by the local presence of the tumor. 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.
Paraneoplastic syndromes can precede a diagnosis of cancer as the first sign of disease, and when recurrent, they are typically a harbinger of relapse.
Although many paraneoplastic syndromes resolve with successful treatment of the underlying cancer, some syndromes persist despite tumor response to treatment and can cause substantial ongoing patient morbidity.
Broadly, paraneoplastic syndromes in small animals can be grouped into the following categories: gastrointestinal, endocrinological, hematologic, cutaneous, neurological, and miscellaneous (hypertrophic osteopathy, fever).
Specific paraneoplastic syndromes are associated with relatively few cancer types, so the list of differential diagnoses for patients with these syndromes can be narrowed.
