Paraneoplastic syndromes are an important and often overlooked extension of cancer. Although they are more commonly recognized and studied in human medicine, paraneoplastic syndromes are often present in our veterinary patients as well, and they may cause more morbidity and mortality than the tumor itself. Whether they are life threatening or only threatening to quality of life, paraneoplastic syndromes often require medical intervention, and it is imperative that we recognize and treat them when they occur.

The definition of PNS is “a neoplasm-associated alteration in bodily structure or function that occurs distant to the tumor.”¹ Usually caused by substances produced by the tumor, PNS can occur in nearly all body systems. Signs of the PNS can be present months or years before discovery of the primary tumor. Often it is the PNS itself that draws our attention, and because of it, we discover the tumor. Many tumors can cause PNS, and the types of disorders are extremely varied.

Gastrointestinal PNS

Cancer Cachexia
Gastrointestinal Ulceration

Endocrine PNS

Hypercalcemia
Hypoglycemia

Hematologic PNS

Anemia
Polycythemia
Eosinophilia

Neurologic PNS

Myasthenia Gravis

Other PNS

Hypertrophic Osteopathy
Fever

Paraneoplastic syndromes encompass a wide array of medical conditions all caused by substances produced by tumor cells. Many times, the PNS is the first sign of disease, leading the medical team on a scavenger hunt to find the neoplasia it is hiding. Unfortunately, oftentimes, it is the PNS itself that is the cause of death. Usually, resolution of the primary tumor is the best treatment for the PNS; however, adjuvant therapies may be helpful. It is important to recognize the telltale signs of PNS, as they are often the most important pieces of the puzzle.