2 forms:single (= osteochondroma) or multicentric (= osteochondromatosis)
Multiple cartilaginous exostoses occurs after skeletal maturity in cats
Mean age 3.2 years
No breed or sex predisposition ± Siamese cats
Etiology: familial or viral with nearly all cats are FeLV-positive)
Multiple cartilaginous exostoses are rarely symmetrical and do not affect long bones, in contrast to dogs
Common sites: scapula, vertebrae, and mandible
FeLV-induced multiple cartilaginous exostoses are rapidly progressive with firm, painful swellings
Survey Radiographs: sessile or pedunculated protuberances from bony surfaces with indistinct borders, loss of smooth contour, and evidence of lysis, particularly with malignant transformation
Lesions are composed of hard irregular exostoses with a fibrous and cartilaginous cap
Endochondral ossification extends from the cap for a variable thickness
Complete surgical resection is difficult as the cap tends to blend with adjacent tissue
Surgery is indicated for palliation but recurrence is common
Multiple cartilaginous exostoses have an aggressive biologic behaviour with potential for malignant transformation and metastases