Also known as: Osteoclastoma
Introduction
This is well-established in humans but rare in animals, with only a few individual cases in dogs and cats.
Species, age or breeds specificities have not been established.
The histogenesis of the tumour is uncertain. The multi-nucleated giant cells which are the hallmark of this disease arise by fusion of proliferating, plump, ovoid to spindle-shaped neoplastic cells comprising the bulk of the tumour mass. These cells have the same enzymatic behaviour as osteoclasts, and the tumours are sometimes called osteoclastomas.
Benign and malignant variations of the tumour exist, although the benign form is thought to be more common.
Clinical Signs
This tumour arises as a painful swelling on the limb. Vertebral, costal and metacarpal lesions can also exist.
It is an expansile, osteolytic lesion, usually near the end of long bones and firmly attached to the underlying bone. The tumour is usually surrounded by a thin shell of bone.
Pathological fractures may occur at the site.
Diagnosis
Biopsy yields a population of large numbers of multinucleated giant cells that ressemble osteoclasts. Their cytoplasmic borders are often indistinct. The tumour is highly vascular and may contain cavernous spaces and areas of haemorrhage. Osteoid production is absent or minimal.
Confusion may arise as osteosarcomas may contain large numbers of giant cells and closely resemble giant cell tumours.
Cytological exam will reveal: a high percentage of multinucleated cells among many plump, spindle-shaped or ovoid mesenchymal cells.
Treatment
Surgical excision is the treatment of choice, and amputation is usually indicated as the tumour is closely attached to underlying bone.
Most tumours are benign, although 50% may recur if only local excision is performed.
10% may metastasise, typically to the lungs, and chemotherapy may be necessary in those cases. The prognosis will be poor.
References
Meuten, D. (2002) Tumours in domestic animals Wiley-Blackwell
Moulton, J. (1978) Tumours in domestic animals University of California Press
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