Felis ISSN 2398-2950

Bone tumor: overview

Contributor(s): Laura Garrett, Jo Morris


  • Cause: lameness, bony swelling.
  • Diagnosis: signs, radiography, histopathology.
  • Treatment: surgery +/- chemotherapy.
  • Prognosis: good for benign lesions, guarded for malignant.
  • Bone cancer is rare in cats.
  • Between 67-90% of bone tumors are histologically malignant but metastasis is less common than in the dog.
    Print off the Owner factsheet on cancer  Cancer in your cat - possible options  to give to your client.



  • It can be primary, ie arising in the bone, or secondary, ie arising from adjacent soft tissues and invading bone or metastatic to bone.
  • Malignant primary tumors include:
    • Osteosarcoma Osteosarcoma (most common ~ 80% of all bone tumors).
    • Parosteal (juxtacortical) osteosarcoma.
    • Chondrosarcoma Chondrosarcoma.
    • Giant cell tumor (osteoclastoma).
    • Rhabdomyosarcoma.
  • Benign primary tumors include:
    • Osteoma.
    • Ossifying fibroma.
    • Chondroma.
    • Osteochondroma/osteochondromatosis.
    • Multiple cartilaginous exostoses Cartilaginous exostosis- MCE (aggressive disease in cats).
  • Secondary bone tumors include:


  • Almost all cats with malignant cartilaginous exostoses are FeLV positive, ie probably viral origin.
  • Osteosarcoma and fibrosarcoma reported at site of long bone fracture after internal fixation - subclinical osteomyelitis (chronic inflammation) may cause malignant transformation.
  • Osteosarcoma (and other sarcomas) also reported at vaccination sites Feline injection-site associated sarcoma (chronic granulomatous reaction to adjuvant may cause malignant transformation).


  • Malignant transformation of cells within bone (osteoblasts, chondroblasts, osteoclasts, etc)   →   uncontrolled proliferation and production of matrix (osteoid or chondroid).
  • Destruction of normal bone   →   lysis and possibly pathological fracture.
  • Metastasis possible, usually late in disease.
  • Benign lesions are well circumscribed and show less disorganization of normal bone structure.
  • May see malignant transformation of benign lesions, eg malignant cartilaginous exostoses, multicentric osteochondroma (osteochondromatosis).
  • Disruption of normal bone structure by cellular proliferation, matrix production and bone destruction causes pain and bony swellings.
  • Reduced weight bearing in limbs and therefore lameness.
  • Surrounding tissues are invaded to some extent and normal joint function may be compromized.
  • Extreme bone lysis in long bones may lead to pathological fracture.
  • Mass affecting ribs may cause dyspnea or pleural effusion.
  • Mass affecting pelvis may cause constipation.
  • Mass in vertebral column may cause paraplegia.
  • Sites can be appendicular or axial skeleton.
  • Some reports say appendicular more common, others say axial.


  • Benign lesions progress slowly - months.
  • Malignant lesions may progress more rapidly - weeks to months.
  • MCE - progresses rapidly.


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login


This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Simon D, Gruber A D, Hewicker-Trautwein M et al (2000) Pathological femoral fracture due to rhabdomyosarcoma in a cat. JSAP 41 (12), 566-570 PubMed.
  • Davidson J R (1995) Canine and feline chondrosarcoma. Comp Cont Ed 17 (9), 1109-1114 VetMedResource.
  • Fry P D & Jukes H F (1995) Fracture associated sarcoma in the cat. JSAP 36 (3), 124-126 PubMed.
  • Bitetto W V, Patnaik A K, Schrader S C et al (1987) Osteosarcoma in cats - 22 cases (1974-1984). JAVMA 190 (1), 91-93 PubMed.
  • Quigley P J & Leedale A H (1983) Tumours involving bone in the domestic cat - a review of 58 cases. Vet Pathol 20 (6), 670-686 PubMed.
  • Liu S K, Dorfman H D & Patnaik A A (1975) Primary and secondary bone tumors in the cat. JSAP 15 (3), 141-156 Wiley Online Library.