Page 1432 - Cote clinical veterinary advisor dogs and cats 4th

726 Osteosarcoma

• Monitor hepatic values if on itraconazole or • Chronic osteomyelitis can recur weeks to Prevention
fluconazole. • Fungal osteomyelitis may require several • Aseptic surgical technique
years after the initial treatment.
VetBooks.ir Possible Complications months of treatment, and outcome is guarded Technician Tips
• Appropriate antimicrobial prophylaxis and
therapy
to poor.
• Bone abscess
• Bacteremia
arthrosis and limb disuse.
• Fracture/limb deformity • Involvement of joints may result in osteo- • Animals with active draining infections should
• Implant failure be isolated to reduce the possibility of cross-
• Cellulitis PEARLS & CONSIDERATIONS contamination of other surgical patients.
• Draining tracts • Disposable gowns, mask, and gloves should
• Delayed/nonunion Comments be worn for wound care/bandage changes.
• Sequestrum formation • Obtaining a culture only from the drainage
tract can be misleading because contaminants Client Education
Recommended Monitoring (skin organisms and gram-negative bacteria) Treatment of chronic osteomyelitis can be costly
• Radiographs at 4-6 week intervals to evaluate are common. and lengthy.
healing • Leukocytosis is common with acute
• Aspirate and reculture if animal shows signs disease; typically it is absent with chronic SUGGESTED READING
of recurrence. infection. Robinson R: Osteomyelitis and implant-associated
• Antibiotic-coated implants are being used infections. In Johnston SA, et al, editors: Veterinary
PROGNOSIS & OUTCOME for prevention and treatment. surgery: small animal, ed 2, St. Louis, 2018, Elsevier,
• Radiographic appearance of fungal osteomy- pp 775-783.
• Acute osteomyelitis can be eradicated with elitis and primary bone tumors is similar. AUTHOR: Mary E. Somerville, DVM, DACVS
early, aggressive treatment. EDITOR: Kathleen Linn, DVM, MS, DACVS

Osteosarcoma Client Education
Sheet

BASIC INFORMATION commonly. In the hindlimb, lesions are are not as consistent as with appendicular
evenly distributed among the distal femur, tumors. Depending on the size and location
Definition proximal tibia, and distal tibia. of the tumor, a mass might or might not be
Osteosarcoma (OSA) is a primary malignant • 25% of OSA arises from the axial skeleton. visible or palpable.
tumor of mesenchymal tissue that always The mandible, maxilla, vertebra, ribs, and
includes the production of bone (osteoid) by pelvis are most commonly affected. Etiology and Pathophysiology
malignant osteoblasts. • Extraskeletal OSA is rare. Mammary gland Cause is largely unknown, but OSA has
is one of the more frequently reported sites. been associated with fracture sites, metallic
Epidemiology orthopedic implants, chronic osteomyelitis,
SPECIES, AGE, SEX HISTORY, CHIEF COMPLAINT bone infarction, osteochondromatosis, and
• In dogs, OSA accounts for up to 85% of • Appendicular OSA usually is associated with ionizing radiation.
all primary bone tumors. progressive lameness. Occasionally, lameness
○ Median age is 7-9 years, with a smaller is acute and severe due to a pathologic DIAGNOSIS
peak incidence at 1.5-2 years of age. fracture. A palpable swelling might or might
○ No obvious sex predisposition not be present. Diagnostic Overview
• In cats, primary bone tumors are uncommon, • Axial OSA can present with a variety of signs. The diagnosis is strongly suspected based on
but OSA accounts for 70%-80% of those Localized swelling with or without pain is patient signalment, history, physical exam find-
seen. common. Tumors arising from the mandible ings, and radiographic evidence of an aggressive
○ Extraskeletal OSA can occur at sites of or maxilla can be associated with halitosis, bone lesion. Cytology can further support the
previous vaccinations (p. 550). dysphagia, pain on opening the mouth, or diagnosis, but histopathology is required for a
nasal discharge. Vertebral tumors may induce definitive diagnosis.
GENETICS, BREED PREDISPOSITION neurologic deficits. Rarely, rib tumors are
• Body size (height and weight) is a more associated with respiratory signs. Differential Diagnosis
important predictor than breed. • The first clinical signs of pulmonary metasta- • Other primary bone tumors: chondrosar-
• Compared with small-breed dogs (weighing sis usually are vague, including lethargy and coma, fibrosarcoma, hemangiosarcoma
< 10 kg [22 lb]), the risk of OSA is 60 times anorexia. The animal may cough, but overt • Metastatic bone tumors: transitional cell,
higher in dogs weighing > 30 kg (66 lb) and respiratory distress is uncommon. Rarely, prostatic, mammary, thyroid, anal sac
8 times higher in dogs weighing 20-30 kg lameness develops in one or more limbs carcinomas, pulmonary carcinoma (cat only)
(44-66 lb). secondary to hypertrophic osteopathy. • Tumors that locally invade adjacent bone:
• Appendicular OSA accounts for 95% of all synovial cell sarcoma, histiocytic sarcoma,
cases in dogs weighing > 40 kg but only PHYSICAL EXAM FINDINGS oral tumors (squamous cell carcinoma [SCC],
40%-50% of all cases in dogs weighing < 15 kg. • Dogs with appendicular OSA exhibit lame- melanoma, fibrosarcoma, ameloblastoma),
ness ranging from minimal to non–weight- digital tumors (SCC, melanoma)
Clinical Presentation bearing. A palpable swelling might or might • Hematopoietic tumors: myeloma, lymphoma.
DISEASE FORMS/SUBTYPES not be present. Radiographic lesions typically are purely
• 75% of OSA arises from the appendicular • Dogs with axial OSA can have variable lytic.
skeleton. In the forelimb, the distal radius physical exam findings (see History, Chief • Bacterial or fungal (e.g., blastomycosis,
and proximal humerus are affected most Complaint). Signs of pain or discomfort coccidioidomycosis) osteomyelitis
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