What Is Your Diagnosis?

Tisha A. M. Harper Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061.

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Jonathan M. Miller Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061.

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Dean E. Filipowicz Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA 24061.

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History

A 7-year-old sexually intact male Boxer was evaluated for a 4-week history of lameness in the left hind limb. The lameness had appeared acutely after moderate outdoor activity. The dog had been treated with nonsteroidal anti-inflammatory medication and cage rest by the referring veterinarian with minimal improvement. On examination, the dog had a toe-touching lameness in the left hind limb. Physical examination revealed crepitus, medial buttress, joint effusion, and signs of moderate discomfort on flexion and extension of the left stifle joint. There was also mild atrophy of the left hind limb musculature. Neither cranial drawer nor cranial tibial thrust signs were elicited during an orthopedic examination performed while the dog was sedated. Findings from a CBC and serum biochemical analyses were unremarkable. Radiographic views of the left stifle joint were obtained (Figure 1).

Figure 1—
Figure 1—

Lateral (A) and craniocaudal (B) radiographic views of the left stifle joint of a 7-year-old sexually intact male Boxer evaluated for a left hind limb lameness of 4 weeks' duration.

Citation: Journal of the American Veterinary Medical Association 232, 5; 10.2460/javma.232.5.681

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Radiographic Findings and Interpretation

Periarticular osteophyte production, cortical remodeling, and stifle joint effusion are evident. There also is a large, aggressive multiloculated osteolytic lesion of the distal femoral metaphysis and soft tissue mineralization medially (Figure 2). Differential diagnoses include a primary bone tumor, such as osteosarcoma, chondrosarcoma, fibrosarcoma, hemangiosarcoma, liposarcoma, giant cell tumor, or plasma cell tumor; multiple myeloma; bacterial or fungal osteomyelitis; or a bone cyst. The lesion could also have been the result of metastasis (eg, prostatic carcinoma, mammary carcinoma, or urinary bladder carcinoma).

Figure 2—
Figure 2—

Same radiographic views as in Figure 1. Notice the periarticular osteophyte production (small black arrowheads), cortical remodeling (white arrowhead), stifle joint effusion (large black arrowhead), and thelarge, aggressive multiloculated osteolyticlesion of the distalfemoralmetaphysis(black arrow). Soft tissue mineralization is also evident medially (white arrow).

Citation: Journal of the American Veterinary Medical Association 232, 5; 10.2460/javma.232.5.681

Comments

Examination of fluoroscopically guided bone biopsy specimens obtained by trephination from the center and periphery of the lesion revealed bone necrosis in the center and transition from normal to necrotic bone at the periphery. Subsequent exploratory arthrotomy revealed a proliferative bony lesion on the medial femoral condyle. Histologic evaluation of a biopsy specimen of this lesion revealed chondrosarcoma. The left hind limb was subsequently amputated, and the diagnosis was confirmed histopathologically. There was no radiographic evidence of metastasis to the lungs.

The findings on physical examination were characteristic of chronic degenerative joint disease in the stifle joint. Medium-to large-breed dogs commonly develop hind limb lameness caused by hip dysplasia or cranial cruciate ligament rupture; however, lameness is also a common clinical sign in dogs with tumors of the appendicular skeleton. Radiography is important in documenting any degenerative changes and to rule other bony abnormalities in or out as a cause of lameness. Radiography is also necessary following a bone biopsy to confirm the correct location of the biopsy site and to document the absence of postprocedural fracture.

Chondrosarcoma accounts for 5% to 10% of canine primary bone tumors,1,2 making it the second most common primary bone tumor in dogs. Osteosarcoma is the most common.3 Although chondrosarcomas are most commonly located in the nasal cavity of dogs, they have been reported to affect long bones, ribs, the pelvis, vertebrae, and facial bones as well as extraskeletal sites such as the trachea, aorta, and lungs.3 Metastasis has been identified in 15% to 28% of affected dogs.4,5 The distal femoral metaphysis is one of the common sites for primary tumors of the appendicular skeleton.6

Radiographic evaluation is a necessary part of the diagnostic plan for primary bone tumors. Radiography is noninvasive and is readily available in most veterinary practices. Bone lesions with an aggressive radiographic appearance may be either neoplastic or infectious. Such lesions cannot be definitively distinguished from each other solely on the basis of radiography, and factors that must be included while making the diagnosis include the history and results of physical examination, microbial cultures, and histologic examination.7 Radiographic views of the affected bones as well as a 4-view radiographic series of the thorax should be evaluated for evidence of metastasis. The presence of a solitary aggressive bone lesion in the metaphyseal region of a middle-aged or older large-breed dog is supportive for a diagnosis of a primary bone tumor and should be considered as such until proven otherwise.7 The next most likely diagnosis for a monostotic aggressive bone lesion is fungal osteomyelitis.7 Fluoroscopy is another imaging modality that was used as part of the diagnostic protocol for the dog of this report. It facilitated a limited surgical approach to obtain initial biopsy specimens within the lesion while allowing direct (real-time) confirmation that the specimens were being obtained from representative areas of the lesion. For the dog of this report, however, a second biopsy specimen was necessary to obtain a definitive diagnosis.

In a recent retrospective study5 on non-nasal chondrosarcoma in dogs, wide surgical excision was found to substantially increase survival time. Death or euthanasia is generally attributed to metastasis, with pulmonary metastasis developing in 20.5% of dogs in 1 study.4 The use of adjuvant radiation therapy or chemotherapy for chondrosarcomas has been reported with varying results.3-5

  • 1

    Brodey RS, Misdorp W, Riser WH, et al. Canine skeletal chondrosarcoma: a clinicopathologic study of 35 cases. J Am Vet Med Assoc 1974;165:6878.

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  • 2

    Sylvestre AM, Brash ML, Atilola MAO, et al. A case series of 25 dogs with chondrosarcoma. Vet Comp Orthop Traumatol 1992;5:1317.

  • 3

    Withrow SJ, Vail DM. Tumors of the skeletal system. In:Withrow and MacEwen’s small animal clinical oncology. 4th ed. St Louis: Saunders Elsevier, 2006;567568.

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  • 4

    Popovitch CA, Weinstein MJ, Goldschmidt MH, et al. Chondrosarcoma: a retrospective study of 97 dogs (1987–1990). J Am Anim Hosp Assoc 1994;30:8185.

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  • 5

    Waltman SS, Seguin B, Cooper BJ, et al. Clinical outcome of nonnasal chondrosarcoma in dogs: thirty-one cases (1986–2003). Vet Surg 2007;36:266271.

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  • 6

    Fossum TW. Other diseases of bones and joints. In:Small animal surgery. 2nd ed. St Louis: Mosby Inc, 2002;11731186.

  • 7

    Thrall DE. Bone tumors versus bone infections. In:Textbook of veterinary diagnostic radiology. 4th ed. Philadelphia: WB Saunders Co, 2002;179186.

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  • Figure 1—

    Lateral (A) and craniocaudal (B) radiographic views of the left stifle joint of a 7-year-old sexually intact male Boxer evaluated for a left hind limb lameness of 4 weeks' duration.

  • Figure 2—

    Same radiographic views as in Figure 1. Notice the periarticular osteophyte production (small black arrowheads), cortical remodeling (white arrowhead), stifle joint effusion (large black arrowhead), and thelarge, aggressive multiloculated osteolyticlesion of the distalfemoralmetaphysis(black arrow). Soft tissue mineralization is also evident medially (white arrow).

  • 1

    Brodey RS, Misdorp W, Riser WH, et al. Canine skeletal chondrosarcoma: a clinicopathologic study of 35 cases. J Am Vet Med Assoc 1974;165:6878.

    • Search Google Scholar
    • Export Citation
  • 2

    Sylvestre AM, Brash ML, Atilola MAO, et al. A case series of 25 dogs with chondrosarcoma. Vet Comp Orthop Traumatol 1992;5:1317.

  • 3

    Withrow SJ, Vail DM. Tumors of the skeletal system. In:Withrow and MacEwen’s small animal clinical oncology. 4th ed. St Louis: Saunders Elsevier, 2006;567568.

    • Search Google Scholar
    • Export Citation
  • 4

    Popovitch CA, Weinstein MJ, Goldschmidt MH, et al. Chondrosarcoma: a retrospective study of 97 dogs (1987–1990). J Am Anim Hosp Assoc 1994;30:8185.

    • Search Google Scholar
    • Export Citation
  • 5

    Waltman SS, Seguin B, Cooper BJ, et al. Clinical outcome of nonnasal chondrosarcoma in dogs: thirty-one cases (1986–2003). Vet Surg 2007;36:266271.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Fossum TW. Other diseases of bones and joints. In:Small animal surgery. 2nd ed. St Louis: Mosby Inc, 2002;11731186.

  • 7

    Thrall DE. Bone tumors versus bone infections. In:Textbook of veterinary diagnostic radiology. 4th ed. Philadelphia: WB Saunders Co, 2002;179186.

    • Search Google Scholar
    • Export Citation

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