Primary bone tumours in the dog and cat can be malignant or benign. The most common benign bone tumours are osteomas and multiple cartilaginous exostoses.
OSTEOMA
Osteoma is an uncommon, benign bone tumour characterized by bone proliferations with a central zone of vascularised osteoid tissue surrounded by an area of sclerotic bone; radiographically the lesion is well defined and histologically it is formed of tissue that is not distinguishable from reactive bone. It is not painful on palpation; however, it may produce lameness when it affects appendicular bones. Forms affecting the skull (zygomatic bone) and limbs (humerus) have been described. Osteomas must be differentiated from multilobular tumour of bone. The treatment of choice is surgery, which is often curative.1,2Osteomas have also been described in the cat.
MULTIPLE CARTILAGINOUS EXOSTOSES
Multiple cartilaginous exostoses are a disease of growing subjects and are thought to have a hereditary aetiology. [5] Lesions develop on bones formed by endochondral ossification (vertebrae, ribs) and their progression stops when skeletal maturity is reached. The exostoses are usually asymptomatic proliferations of mature bone and cartilage and are often incidental findings during diagnostic examinations carried out for other purposes. The lesions, often multiple, may continue to progress even after skeletal maturity, and in such cases malignant transformation should be suspected, as reported in the literature.3 In view of this, it is advisable to follow-up the evolution of the lesion with periodic examinations.
Affected dogs have compact swellings, which are variably painful on palpation and which can produce lameness or neurological symptoms as a result of the mechanical impingement of the mass on adjacent soft tissues or nerve endings.
Histologically the lesions are characterized by a central bone core, covered by a cartilaginous capsule from which mature bone grows. The cortical surfaces of the adjacent bone and of the lesion merge.
In the case of persistent pain the lesions may be removed surgically, once skeletal maturity has been reached.2,4
In the cat, unlike in the dog, the lesions develop after skeletal maturity has been reached and usually develop in the long bones; these lesions have a locally aggressive behaviour. No predisposition for sex or breed has been found. The origin is assumed to be viral and cats must be tested for feline leukaemia virus.2
References
- Dernell, W.S., Ehrhart, N.P., Straw, R.C., Vail, D.M., 2007. Tumors of the skeletal system. In: Withrow, S.J., Vail, D.M. (Eds.), Withrow and MacEwen’s Small Animal Clinical Oncology. Saunders, Elsevier, St. Louis, MI, USA, pp. 540-582.
- Gorra, M., Burk, R.L., Greenlee, P., Weeren, FR., 2002. Osteoid osteoma in a dog .Veterinary Radiology and Ultrasound43(1),28-30.
- Green, E.M., Adams, W.M., Steinberg, H., 1999. Malignant transformation of solitary spinal osteochondroma in two mature dogs. Veterinary Radiology and Ultrasound40(6),634-7.
- Jacobson, L.S., Kirberger, R.M., 1996. Canine multiple cartilaginous exostoses: unusual manifestations and a review of the literature. Journal of American Animal Hospital Association 32(1),45-51.