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Siddharth A. Ranade Fifth Avenue Veterinary Specialists, 1 W 15th St, New York, NY 10011.

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Philip D. Pacchiana Fifth Avenue Veterinary Specialists, 1 W 15th St, New York, NY 10011.

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 DVM, MS, DACVS

History

A 16-year-old castrated male domestic shorthair cat was evaluated for progressive right hind limb lameness of 3 years' duration. On physical examination, the cat had a grade 1 to 2 (out of 4) lameness of the right hind limb. Palpation revealed decreased adduction of the limb and a firm 5- to 6-cm-diameter immovable mass emanating from the ventral aspect of the pubis, interfering with adduction of the limb. Findings on rectal examination and thoracic radiography were unremarkable. Radiographs of the pelvis were obtained (Figure 1).

Figure 1—
Figure 1—

Lateral (A) and ventrodorsal (B) radiographic views of the pelvis of a 16-year-old castrated male domestic shorthair cat with lameness of 3 years' duration.

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1243

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

Radiographic Findings and Interpretation

An irregularly marginated, mineralized mass appears to originate from the right pubis and project ventrally. Spondylosis is present at the lumbosacral junction. The mass appears to be interfering with the right hip joint (Figure 2). On the basis of the radiographic findings, differential diagnoses for the mass include benign or malignant neoplasia and osteomyelitis.

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Notice the irregular mineralized mass evident at the junction of the right pubis, acetabulum, and caudal aspect of the ilium (arrows). Also, notice the spondylosis of the vertebrae at the lumbosacral junction (small arrows).

Citation: Journal of the American Veterinary Medical Association 238, 10; 10.2460/javma.238.10.1243

Comments

The presence of a mineralized radiopaque mass is consistent with a lesion of bone or cartilaginous origin. The radio-graphic appearance (proliferative), large size of the mass, and location of the mass are most consistent with a solitary osteochondroma. However, other less likely considerations include osteoma, osteosarcoma, osteochondrosarcoma, chondroma, chondrosarcoma, and osteomyelitis of bacterial, fungal, viral, or parasitic origin. In cats, FeLV and feline fibrosarcoma virus—feline oncorna virus have been linked with osteochondromatosis.1,2 Viral origins have not been shown to be causal in cats with solitary osteochondromas.2

The mass was excised. Postoperatively, the cat did well in the hospital and was discharged. The mass had a peripheral cap of fibrous and cartilaginous tissue. Spicules of bone had developed from endochondral-like ossification of cartilage columns, predominantly of collagenous extracellular matrix in the medullary region. The histopathologic diagnosis was a solitary osteochondroma.1–4

Osteochondromatosis is also known as multiple osteochondromas, multiple hereditary exostoses, multiple cartilaginous exostoses, multiple osteochondromatosis, diaphyseal aclasis, and hereditary chondrodysplasia.1,4

Radiographically, osteochondromatosis has been noted to have several variations, including solitary spinal masses, sessile bulges from bones with clear and smooth to amorphous margins, and linear masses parallel to long bones with no osseous attachment.1,5 In dogs, radiologic forms also include symmetric, semiannular, and annular osteochondromas and have been associated with limb shortening and angular deformities.4

Most patients are examined because of lameness or neurologic signs.1–5 In humans, dogs, and horses, osteochondromatosis usually originates at the physes and masses cease to grow at the time of physeal closure. In cats, the lesion can occur at multiple or single sites in the body at any age. Another specific difference in cats, compared with other species, is that the lesions progress and continue to grow.2 No breed predispositions or hereditary patterns have been reported in cats, although osteochondromatosis may be an autosomal dominant inherited trait in humans, dogs, and horses.1,4,5 The prognosis may be good to guarded depending on progression of disease or its location. Malignant transformation to osteosarcoma and viral etiologies have been reported.1,4,5 However, the cat of this report did well after surgery.

Computed tomography or magnetic resonance imaging can be useful to delineate margins, characterize the lesion, plan surgery, and assist in prognosis. Excision with wide margins is the treatment of choice.1,2,4

  • 1.

    Levitin BAroch IAizenberg I, et al. Linear osteochondromatosis in a cat. Vet Radiol Ultrasound 2003; 44:660664.

  • 2.

    Turrel JMPool RR. Primary bone tumors in the cat: a retrospective study of 15 cats and a literature review. Vet Radiol Ultrasound 1982; 23:152166.

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  • 3.

    Kirberger RMDewald KFWagner WM. Radiological abnormalities of the appendicular skeleton of the lion (Panthera leo): incidental findings and Mycobacterium bovis-induced changes. Vet Radiol Ultrasound 2006; 47:145152.

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  • 4.

    Mozos ENovales MGinel PJ, et al. A newly recognized pattern of canine osteochondromatosis. Vet Radiol Ultrasound 2002; 43:132137.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Green EMAdams WMSteinberg H. Malignant transformation of solitary spinal osteochondroma in two mature dogs. Vet Radiol Ultrasound 1999; 40:634637.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Lateral (A) and ventrodorsal (B) radiographic views of the pelvis of a 16-year-old castrated male domestic shorthair cat with lameness of 3 years' duration.

  • Figure 2—

    Same radiographic images as in Figure 1. Notice the irregular mineralized mass evident at the junction of the right pubis, acetabulum, and caudal aspect of the ilium (arrows). Also, notice the spondylosis of the vertebrae at the lumbosacral junction (small arrows).

  • 1.

    Levitin BAroch IAizenberg I, et al. Linear osteochondromatosis in a cat. Vet Radiol Ultrasound 2003; 44:660664.

  • 2.

    Turrel JMPool RR. Primary bone tumors in the cat: a retrospective study of 15 cats and a literature review. Vet Radiol Ultrasound 1982; 23:152166.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Kirberger RMDewald KFWagner WM. Radiological abnormalities of the appendicular skeleton of the lion (Panthera leo): incidental findings and Mycobacterium bovis-induced changes. Vet Radiol Ultrasound 2006; 47:145152.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Mozos ENovales MGinel PJ, et al. A newly recognized pattern of canine osteochondromatosis. Vet Radiol Ultrasound 2002; 43:132137.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5.

    Green EMAdams WMSteinberg H. Malignant transformation of solitary spinal osteochondroma in two mature dogs. Vet Radiol Ultrasound 1999; 40:634637.

    • Crossref
    • Search Google Scholar
    • Export Citation

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