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Chondrosarcoma 165

• One dose of activated charcoal (1-2 g/kg) Drug Interactions PEARLS & CONSIDERATIONS
with cathartic, followed by cholestyramine Avoid Ca-containing fluids. Comments
300 mg/kg PO q 8h for 4 days. Cholestyr-
VetBooks.ir amine is a resin that binds bile acids and Possible Complications • 1 IU of vitamin D 3 = 0.000025 mg Diseases and Disorders
disrupts the enterohepatic recirculation of
• Calcification of soft tissues (irreversible):
• Prescription strength vitamin D is available
vitamin D.
• If Ca is increasing, promote calciuresis: chronic kidney disease, arrhythmias, in 50,000 IU (1.25 mg).
aneurysms
0.9% NaCl IV (adjust rates as needed); • Pulmonary edema (mineralization and Prevention
furosemide 2.5-4.5 mg/kg PO, IM, or IV leakage of pulmonary vessels) Prevent pet access to all vitamin D or analog-
q 6-8h; prednisolone 1-2 mg/kg/day PO containing products.
divided Recommended Monitoring
• Hyperphosphatemia: aluminum (or mag- Follow serum Ca, PO 4, BUN, and creatinine Technician Tips
nesium) hydroxide 30-90 mg/kg/day PO levels daily, then weekly until they remain Many times, anorexia or vomiting is the first
divided normal without medical support. If no eleva- indication that the serum Ca is increasing.
• If still hypercalcemic after all of the above: tions by day 4, therapy can be stopped.
pamidronate 1.3-2 mg/kg IV over 2 hours; Client Education
repeat in 3-7 days if needed (caution in PROGNOSIS & OUTCOME Pet proofing is important for medications and
juveniles) rodenticides.
• Address acute kidney injury (p. 23). • Good prognosis if animal is decontaminated
and treated before persistent hypercalcemia SUGGESTED READING
Chronic Treatment and soft-tissue mineralization occurs. Rumbeiha WK: Cholecalciferol. In Peterson ME,
Several days to weeks of oral therapy may be • Prognosis is poor to guarded with prolonged et al, editors: Small animal toxicology, ed 3, St.
needed until Ca normalizes. elevations in Ca, leading to soft-tissue Louis, 2013, Saunders, pp 489-498.
mineralization. Tissue calcification is not
Nutrition/Diet reversible and can lead to chronic GI or AUTHOR & EDITOR: Tina Wismer, DVM, MS, DABVT,
With anorexia, use of feeding tubes may be renal issues and potentially rupture of great DABT
indicated (p. 1106). Use diet low in Ca and vessels (aneurysm).
PO 4 , such as a renal diet.

Chondrosarcoma Client Education
Sheet

BASIC INFORMATION all nasal tumors, and 20% of CSAs arise tumors may be associated with a visible
from the ribs, accounting for 30%-40% of mass effect (externally or orally). The ipsi-
Definition all primary rib tumors. lateral eye may not retropulse or may be
Chondrosarcoma (CSA) is a malignant mes- • Of CSAs, 20% arise from the appendicular exophthalmic.
enchymal tumor that produces chondroid and skeleton, often but not always at sites where • Rib CSA most commonly arises near the
fibrillar matrix but never osteoid. osteosarcoma typically occurs. CSA accounts costochondral junction. Any rib can be
for only 3%-5% of all primary bone tumors affected.
Epidemiology in the appendicular skeleton. • Patients with appendicular and digital CSA
SPECIES, AGE, SEX • Other reported sites include facial bones, are variably lame, ranging from minimal to
• In dogs, CSA is the second most common skull, vertebrae, pelvis, digits, and os penis. non–weight-bearing.
primary bone tumor, accounting for 5%-10% • Rarely, CSA can arise in soft-tissue (extraskel-
of all primary bone tumors. etal) sites, including the larynx and trachea. Etiology and Pathophysiology
○ Median age is about 8 years (reported The cause is largely unknown. Osteochondro-
range, 1-15 years). HISTORY, CHIEF COMPLAINT matosis (multiple cartilaginous exostoses) lesions
○ There is no sex predisposition. • Patients often present with a visible mass can undergo malignant transformation to CSA
• In cats, primary bone tumors are uncom- at the affected site. Additional clinical signs or, less commonly, osteosarcoma.
mon, and CSA is third in incidence behind vary with the site of involvement.
osteosarcoma and fibrosarcoma. CSA also can • Nasal CSA usually is associated with unilat- DIAGNOSIS
occur in the soft tissues at sites of previous eral or bilateral epistaxis. Other clinical signs
vaccinations (p. 550). include sneezing, mucopurulent discharge, Diagnostic Overview
respiratory effort, and swelling over the nasal CSA is not the most common primary bone
GENETICS, BREED PREDISPOSITION cavity. tumor, but it still should be considered as a
• CSA is most common in medium- to large- • Appendicular CSA usually is associated with differential when an aggressive bone lesion is
breed dogs weighing 20-40 kg. lameness. identified, especially when the lesion involves
• Mixed-breed dogs, golden retrievers, the rib or nasal cavity. Histopathology is
boxers, and German shepherd dogs are PHYSICAL EXAM FINDINGS required for definitive diagnosis.
overrepresented. • Findings for CSA will depend on the
anatomic location. Often, but not always, Differential Diagnosis
Clinical Presentation a firm to hard mass will be palpable. General differential diagnoses for aggressive
DISEASE FORMS/SUBTYPES • Patients with nasal CSA often have reduced bone lesions:
• Most CSAs arise from flat bones: 30% occur airflow through the nares, and hemorrhagic • Other primary bone tumors: osteosarcoma,
in the nasal cavity, accounting for 15% of discharge might be present. More advanced fibrosarcoma, hemangiosarcoma

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