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Paraneoplastic Syndromes
Cory Brown, DVM, DACVIM (SAIM)

VetScan Mobile Diagnostics, Powell, OH, USA

Many tumors produce effects on the body that are not bone invasion resulting in increased osteolysis and
related to direct invasion or compression. These effects production of osteoclast‐activating factor by tumor cells.
have become widely recognized as paraneoplastic syn-
dromes. Recognition and treatment of these conditions
may allow early detection of occult neoplasia, reduction Diagnosis
of morbidity, and prolonged survival. The effects of par- Initial investigation should include a thorough physical
aneoplastic syndromes are due to the production and and rectal examination. Further diagnostic evaluation
excretion of peptides and hormones as well as immune should include thoracic radiographs and abdominal radi-
cross‐reaction between tumor and normal cells. This ographs or ultrasonography. Ultrasonography is pre-
chapter describes the most commonly recognized ferred to evaluate for diffuse infiltration of abdominal
paraneoplastic syndromes and their treatment. It is organs as well as abdominal lymphadenomegaly, as these
important to recognize that the most effective treat- may be difficult to appreciate radiographically. Aspiration
ment for all paraneoplastic syndromes is removal of the of peripheral lymph nodes may be useful, even when the
underlying tumor. lymph nodes are not clinically enlarged. Bone marrow
aspiration may be considered, especially in the face of
peripheral cytopenias, and additional radiographs or
Hypercalcemia bone scintigraphy may be carried out based on the
presence of lameness or discomfort encountered during
Etiology/Pathophysiology palpation of long bones. Confirmation of an elevated cal-

Hypercalcemia remains one of the most commonly cium secondary to malignancy may be attempted by
encountered paraneoplastic syndromes in the dog and evaluating PTH, PTH‐rp, and ionized calcium levels in
cat. Commonly termed “humoral hypercalcemia of the serum. It is important to note that the ionized
malignancy,” this condition must be differentiated from calcium level is increased in patients with humoral
other common causes of hypercalcemia. Although it is hypercalcemia of malignancy, and this may be moni-
often noted with lymphoma (particularly mediastinal tored for a more accurate assessment of bioactive cal-
lymphoma), multiple myeloma and anal sac adenocarci- cium levels. Evaluation of PTH‐rp with ionized calcium
noma, it may be observed with a variety of tumors. The and PTH can also help differentiate humoral hypercalce-
most common mechanism resulting in hypercalcemia is mia of malignancy from other causes of hypercalcemia
release of a peptide by the tumor cells closely resembling (i.e., renal disease, hyperparathyroidism).
parathyroid hormone (PTH), called parathyroid hor-
mone‐related protein (PTH‐rp). PTH‐rp mimics the Treatment
activity of PTH by binding to PTH receptors within the
renal tubule and bone. This leads to decreased calcium Common symptoms of hypercalcemia include polyuria/
excretion from the kidney and increased bone resorp- polydipsia, muscle tremors, neurologic abnormalities
tion. Other factors involved in hypercalcemia not related (including coma), renal dysfunction, and inappetence.
to humoral hypercalcemia of malignancy include direct Treatment is aimed at reducing the ionized calcium level

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical