History
A 4-year-old castrated male domestic medium hair cat was evaluated because of a 2-week history of progressive right hind limb lameness, difficulty jumping, decreased appetite, and constipation. No abnormalities were detected on CBC and serum biochemical analysis. Serologic results of FeLV antigen testing, FIV antibody testing, and Toxoplasma antibody testing were negative. No abnormalities were evident on thoracic radiographs. Prior treatment with SC fluid therapy, corticosteroids, stool softeners, and enemas did not improve the patient's clinical signs.
Physical examination revealed a body condition score of 7 of 9, firm feces detected on abdominal palpation, weight-bearing right hind limb lameness, and signs of pain on manipulation of the right hip joint. Findings on neurologic examination were unremarkable. Abdominal and pelvic radiographs were obtained (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 4-year-old castrated male domestic medium hair cat that was evaluated because of a 2-week history of progressive right hind limb lameness, decreased appetite, and constipation.
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 4-year-old castrated male domestic medium hair cat that was evaluated because of a 2-week history of progressive right hind limb lameness, decreased appetite, and constipation.
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 4-year-old castrated male domestic medium hair cat that was evaluated because of a 2-week history of progressive right hind limb lameness, decreased appetite, and constipation.
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Radiographic Findings and Interpretation
A monostotic lesion is evident at L7 with extensive remodeling and smooth bony proliferation along the ventral aspect of the vertebral body (Figure 2). There is collapse of the intervertebral disk space at L6-7, the ventral lamina of L7 appears irregular, the left pedicle is destroyed, and the right pedicle is deformed. The caudal vertebral end plate of L6 remains normal in appearance, with no evidence of lesion involvement. There is a moderate amount of feces evident within the colon. The rest of the musculoskeletal and abdominal structures are normal in appearance. Radiographic differential diagnoses included neoplasia (primary or metastatic), osteomyelitis (bacterial or fungal), or previous trauma.
Same lateral and ventrodorsal radiographs as in Figure 1. Notice the marked remodeling of L7 with smooth bony proliferation along the ventral aspect of the vertebral body (thick arrow). There is collapse of the L6-7 intervertebral disk space (thin arrow). The left pedicle is destroyed, and the right pedicle is deformed (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Same lateral and ventrodorsal radiographs as in Figure 1. Notice the marked remodeling of L7 with smooth bony proliferation along the ventral aspect of the vertebral body (thick arrow). There is collapse of the L6-7 intervertebral disk space (thin arrow). The left pedicle is destroyed, and the right pedicle is deformed (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Same lateral and ventrodorsal radiographs as in Figure 1. Notice the marked remodeling of L7 with smooth bony proliferation along the ventral aspect of the vertebral body (thick arrow). There is collapse of the L6-7 intervertebral disk space (thin arrow). The left pedicle is destroyed, and the right pedicle is deformed (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Treatment and Outcome
The cat was hospitalized for rehydration, supportive care, and pain management. The owners declined further diagnostic testing, including CT, MRI, or fine-needle aspiration and biopsy of the lesion. The patient was discharged from the hospital. The cat received 2 weeks of treatment with prednisone (0.5 mg/kg [0.23 mg/lb], PO, q 24 h), buprenorphine (0.015 mg/kg [0.007 mg/lb], PO, q 8 h), famotidine (0.4 mg/kg [0.18 mg/lb], PO, q 12 h), and lactulose (0.5 mL/kg [0.23 mL/lb], PO, q 8 to 12 h). The owner reported that the patient's clinical signs completely resolved with treatment.
The patient was returned to the hospital at 11 months after the initial evaluation because of a 1-week history of recurrent and more severe right hind lameness, new right hind limb conscious proprioceptive deficits, and progressive signs of pain in the lumbar area. Radiographs of the lumbosacral area revealed the progressive and aggressive nature of the lesion (Figure 3), which was consistent with neoplasia or osteomyelitis. Fluoroscopic-guided fine-needle aspirates of the osseous lytic tissues at L7 were obtained with the patient anesthetized. Findings on cytologic evaluation were consistent with a malignant mesenchymal tumor.
Lateral (A) and ventrodorsal (B) survey lumbosacral spinal radiographs of the same cat as in Figure 1 obtained 11 months later. Notice the progressive expansile bony destruction of the seventh lumbar vertebra with complete dorsal lamina obliteration (arrows). There is now bony proliferation of the right pedicle and pathological fracture with collapse of the left side of the vertebral body of L7 (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Lateral (A) and ventrodorsal (B) survey lumbosacral spinal radiographs of the same cat as in Figure 1 obtained 11 months later. Notice the progressive expansile bony destruction of the seventh lumbar vertebra with complete dorsal lamina obliteration (arrows). There is now bony proliferation of the right pedicle and pathological fracture with collapse of the left side of the vertebral body of L7 (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
Lateral (A) and ventrodorsal (B) survey lumbosacral spinal radiographs of the same cat as in Figure 1 obtained 11 months later. Notice the progressive expansile bony destruction of the seventh lumbar vertebra with complete dorsal lamina obliteration (arrows). There is now bony proliferation of the right pedicle and pathological fracture with collapse of the left side of the vertebral body of L7 (arrowheads).
Citation: Journal of the American Veterinary Medical Association 243, 3; 10.2460/javma.243.3.329
The owners declined further care, including more aggressive pain management, chemotherapy, or palliative radiation therapy, and elected for euthanasia. Necropsy revealed a large solitary nodular mass within the dorsal aspect of the soft tissues adjacent to and associated with L7 with no evidence of gross metastatic disease. Nerve ganglia and fibers were variably degenerated because of tumor compression, likely causing the patient's neurologic signs. Histologic examination also confirmed frequent tumor osteoid and highly mitotic spindle-shaped cells infiltrating the adjacent vertebral bone, warranting a diagnosis of osteosarcoma. Ultimately, the histologic findings could not be used to confirm whether the tumor originated in bony or soft tissue structures. The monostotic nature of the radiographic findings and the patient's clinical progression were considered most consistent with osteosarcoma of bony origin.
Comments
Although osteosarcoma is the most common primary bone tumor in cats, it is rare, accounting for < 6% of all neoplasms.1,2 Even rarer in feline patients is the occurrence of osteosarcoma in the axial skeleton, particularly the vertebral column.1,3,4 Extraskeletal osteosarcoma in cats has been reported for visceral organs, eyes, and mammary glands and in subcutaneous tissues in areas of previous injection.1,3 In general, osteosarcoma in cats has a lower metastatic potential, compared with its canine counterpart, and if tumor location permits removal, complete resection can be curative.1,3 Adjunctive chemotherapy or radiation therapy may contribute to longer survival time in feline patients with nonresectable tumors.3,5
Radiographic features of osteosarcoma in cats are variable. One study6 in cats found that axial osteosarcoma was more likely to have a sclerotic radiographic appearance rather than lysis. Additionally, aggressive periosteal proliferation, often seen in dogs with osteosarcoma, is not a common radiographic feature of osteosarcoma in cats.4 In the case described in the present report, CT and MRI would have been beneficial advanced imaging modalities for further evaluation of precise tumor location, spinal cord compression, and pathological changes.
1. Dimopoulou M, Kirpensteijn J & Moens H, et al. Histologic prognosticators in feline osteosarcoma: a comparison with phenotypically similar canine osteosarcoma. Vet Surg 2008; 37: 466–471.
2. Engle GC, Brodey RS. A retrospective study of 395 feline neoplasms. J Am Anim Hosp Assoc 1969; 5: 21–31.
3. Heldmann E, Anderson M, Wagner-Mann C. Feline osteosarcoma: 145 cases (1990–1995). J Am Anim Hosp Assoc 2000; 36: 518–521.
4. Turrel J, Pool R. Primary bone tumors in the cat: a retrospective study of 15 cats and a literature review. Vet Radiol 1982; 23: 152–166.
5. Bitetto WV, Patnaik AK & Schrader SC, et al. Osteosarcoma in cats: twenty-two cases (1974–1984). J Am Vet Med Assoc 1987; 190: 91–93.
6. Kessler M, Tassani-Prell M & von Bomhard D, et al. Feline osteosarcoma: epidemiologic, clinical and radiographic findings in 78 cases (1990–1995) [in German]. Tierarztl Prax 1997; 25: 275–283.
