Paraneoplastic disorders in dogs with hematopoietic tumors

Often overlooked in the presence of neoplasia, PNDs constitute significant clinical entities in dogs with hematopoietic tumors. They may cause morbidity and mortality in such patients, with effects more severe than those caused by the associated tumor. Accurate clinical evaluation of these disorders is important in differential diagnosis and treatment, for failure to realize that cancer can produce many clinical signs similar to those of other diseases may lead to incorrect diagnosis and delayed therapy. Early recognition of the problem underlying the PND is essential to selecting the proper therapeutic approach and maximizing the patient's chances for remission and survival. The presence of these disorders may complicate or rule out the preferred therapy in some cases of hematopoietic neoplasia, because the addition of cytotoxic drugs may worsen the existing PND, predisposing the dog to a variety of complications. Appropriate management of the PND may be of more immediate importance than treatment of the tumor. The study and recognition of PNDs in dogs with hematopoietic tumors may be valuable for a number of reasons: to facilitate early diagnosis of the tumor, for the observed abnormalities may represent tumor cell markers; to allow assessment of premalignant states; to aid in the search for metastases; to help quantify and monitor response to therapy; to aid in the evaluation of tumor recurrence or progression; to aid in identifying specific pathophysiologic processes by which cancer produces systemic effects; and to provide insight into the study of malignant transformation. Recognition of PNDs is relevant to the diagnosis and treatment of many problems in veterinary cancer medicine. With increasing emphasis on diagnosis and treatment of canine hematopoietic tumors, PNDs will be recognized with greater frequency and will assume greater importance in the therapeutic management of those patients. Research in veterinary and human cancer medicine needs to be directed toward identifying more definitively those substances and pathways that are responsible for PNDs, because therapy directed toward arresting the specific pathophysiologic processes causing the PND may offer the best approach for successful management of cancer.