Pulse - March 2023 - 11

PRACTICAL PATHOLOGY
Giant Cell Osteosarcoma
in Dogs
Farshid Shahriar DVM, PhD, Dipl ACVP - Lab For Pets, Tustin, CA
Medical history and clinical findings:
Amputated leg from a dog was submitted for a bone neoplasm in distal
stifle. Growth was approximately 5x4x7 cm located at proximal tibia.
Growth had uneven surface with large areas of soft lytic bones. Tissue
was placed in decal solution and multiple sections were examined.
Histopathologic findings:
The sections from the proximal tibial bone biopsy specimens exhibit
evidence of an osteosarcoma with tumor osteoid and bone formation
and no chondroid differentiation (Fig. 1). The osteosarcoma is simple,
poorly productive, poorly differentiated type and high grade IIIb with
18 mitotic figures/10hpfs and moderate tumor cell atypia. It exhibits
a predominantly fibroblastic cell type composed of sheets of pleomorphic
spindle shaped tumor cells (Fig. 2) with 23 multinucleate tumor
giant cells/10hpfs. (Fig. 3) Tumor cells are pleomorphic, spindle
shaped with large, variably sized, vesicular, irregular, ovoid to spindle
nuclei with one or more large nucleoli, and little to moderate amphophilic
cytoplasm with foci of tumor osteoid and bone formation. The
tumor cell: matrix ratio is approximately 15:1. There is multifocal, severe,
acute hemorrhage and caseous necrosis. There is skeletal muscle
invasion by tumor cells.
Diagnosis:
Diagnosis of poorly differentiated high grade fibroblastic giant cell rich
osteosarcoma was made.
Discussion:
Osteosarcomas of the appendicular skeleton/ medullary origin frequently
metastasize within 6 months of diagnosis. 60% metastasize to
the lungs and 40% metastasize to other musculoskeletal sites. Thoracic
and abdominal radiographs/imaging for evidence of metastasis are warranted.
Evaluate for possible additional axial or appendicular osteosarcomas
at other sites. In some dogs with osteosarcoma, there is a genetic
predisposition to tumor development in certain family lines. Dogs with
Osteosarcoma have been found to have aberrations of the p53 tumor
suppressor gene. Ionizing radiation, chemical carcinogens, fractures/ degenerative
joint disease, infections (e.g. Spirocerca lupi in esophageal
osteosarcomas in dogs, DNA viruses -polyomavirus and SV-40 virus
and RNA viruses -type C retroviruses have been found to induce OSA
in lab animals), foreign bodies and other factors play a role in some affected
species. Giant cell rich osteosarcoma is a rare histological variant
of conventional osteosarcoma commonly presenting in long bones of appendicular
skeleton. P
Figure 1
Figure 2
Figure 3
PULSE
MARCH 2023
11

Pulse - March 2023

Table of Contents for the Digital Edition of Pulse - March 2023

Pulse - March 2023
Chapter Meetings & Calendar
President's Perspective
Pulsepoints
SCVMA Profile
Dimensions in Surgery + Critical Care
Practical Pathology
New President, Board Installed at SCVMA Annual Celebration
UC Davis Update
Tools for Success
Angel Fund
The RVT
Industry Insights
AVMA Diplomates
Digital Photography for Veterinarians
Resources
Disease Table
From the SCVMA Office
Pulse - March 2023 - Pulse - March 2023
Pulse - March 2023 - Cover2
Pulse - March 2023 - 1
Pulse - March 2023 - 2
Pulse - March 2023 - Chapter Meetings & Calendar
Pulse - March 2023 - President's Perspective
Pulse - March 2023 - Pulsepoints
Pulse - March 2023 - 6
Pulse - March 2023 - 7
Pulse - March 2023 - SCVMA Profile
Pulse - March 2023 - Dimensions in Surgery + Critical Care
Pulse - March 2023 - 10
Pulse - March 2023 - Practical Pathology
Pulse - March 2023 - New President, Board Installed at SCVMA Annual Celebration
Pulse - March 2023 - 13
Pulse - March 2023 - UC Davis Update
Pulse - March 2023 - Tools for Success
Pulse - March 2023 - 16
Pulse - March 2023 - Angel Fund
Pulse - March 2023 - The RVT
Pulse - March 2023 - Industry Insights
Pulse - March 2023 - AVMA Diplomates
Pulse - March 2023 - Digital Photography for Veterinarians
Pulse - March 2023 - 22
Pulse - March 2023 - 23
Pulse - March 2023 - 24
Pulse - March 2023 - Resources
Pulse - March 2023 - Disease Table
Pulse - March 2023 - 27
Pulse - March 2023 - 28
Pulse - March 2023 - 29
Pulse - March 2023 - 30
Pulse - March 2023 - 31
Pulse - March 2023 - 32
Pulse - March 2023 - 33
Pulse - March 2023 - 34
Pulse - March 2023 - 35
Pulse - March 2023 - 36
Pulse - March 2023 - 37
Pulse - March 2023 - 38
Pulse - March 2023 - 39
Pulse - March 2023 - 40
Pulse - March 2023 - 41
Pulse - March 2023 - 42
Pulse - March 2023 - 43
Pulse - March 2023 - From the SCVMA Office
Pulse - March 2023 - Cover3
Pulse - March 2023 - Cover4
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