• Cause: osteosarcoma is an aggressive malignant neoplasm arising from transformed primitive cells of mesenchymal origin, ie a sarcoma. These appear to be rare in reptiles but should be considered as differential diagnoses for bony swellings and limb pain.
• Signs: swelling and pain associated with a bony structure but rarely can be associated with soft tissue structures (extra-skeletal osteosarcoma). Lameness and pain may be the first clinical signs noted.
• Diagnosis: radiography and biopsy for histopathology if feasible. Deep core biopsies are needed as extensive periosteal reaction around such lesions can mask the underlying cause.
• Treatment: amputation or excision of the affected limb/bone if feasible. Complete resection of diagnosed soft tissue mass. Chemotherapy has not been extensively used in reptiles and information on this is negligible.
• Prognosis: guarded as such neoplasms are aggressive and malignant with metastasis thought to be common. Non-limb osteosarcomas such as those associated with vertebrae may not be amenable to surgical excision. The pain associated with the primary bone neoplasia can be extremely hard to control.

• Swelling and pain associated with usually a limb, although rarely other sites can be affected, eg vertebrae.
• Lameness.
• Non-specific signs such as lethargy, poor appetite and weight loss.

• Sudden onset swelling of a limb/elsewhere on the skeleton.
• Often marked pain and lameness associated with this swelling.

• Worldwide.

• Rare so none apparent.

• None apparent.

• Appears very rare in reptiles so as yet none apparent.

• The costs of investigations such as diagnostic imaging (radiography Radiography: digital/CT), histopathology from biopsy Biopsy overview or whole-limb sparing surgery or (amputation Digit/limb amputation) and staging for metastases should be discussed with the client.

• Metastatic disease may affect anesthetic risk, depending on the location of metastases.
• Pathological fractures may occur during biopsy sampling of bony lesions for histopathological examination.

• Malignant transformation of primitive mesenchymal cells within bone causing a primary bone neoplasm. Metastasis is thought to be common.
• Very rarely, extra-skeletal sites may be affected.
• Osteosarcomas are rare in reptiles:
  • Indeed, none were found in a recent detailed retrospective study of UK lizard neoplasms.
  • The literature is dominated by single-case reports that include:
    • Osteosarcoma of a vertebra and proximal ribs in a California mountain kingsnake.
    • Osteosarcoma of the axial skeleton of a Woma python.
    • Presumed osteosarcoma in the vertebra of a South American coral snake.
    • An osteochondrosarcoma in the cervical area of a yellow tree monitor.
    • Chondroblastic osteosarcoma arising from the pelvic girdle in two juvenile, related spin-tailed monitor lizards
    • And a similar tumor in a desert monitor lizard which had metastases to the tail, ribs and femur.

• Transformation of primitive mesenchymal bone cells to develop into an aggressive primary bony neoplasm.

• The timecourse of disease in reptiles is unclear due to the scarcity of case reports.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Hall A S, Jacobs J L & Smith E N (2020) Possible osteosarcoma reported from a new world elapid snake and review of reptilian bony tumors. Anat Rec 303 (12), 2955-2966 PubMed.
• Kubiak M, Denk D & Stidworthy M F (2020), Retrospective review of neoplasms of captive lizards in the United Kingdom. Vet Rec 186 (1), 28-28 PubMed.
• Dietz J, Heckers K O, Pees M & Aupperle H (2015) Knochentumoren bei Echsen und Schlangen. Ein seltener klinischer Befund in der Reptilienpraxis [Bone tumours in lizards and snakes. A rare clinical finding]. Tierarztl Prax Ausg K Kleintiere Heimtiere. 43 (1), 31-39 PubMed.
• Needle D, McKnight C A & Kiupel M (2013) Chondroblastic osteosarcoma in two related spiny-tailed monitor lizards (Varanus acanthurus). J Exotic Pet Med 22 (3), 265-269 VetMedResource.
• Cowan M, Monks D & Raidal S (2011) Osteosarcoma in a woma python (Aspidites ramsayi). Aust Vet J 89 (12), 520-523 PubMed.
• Latimer K S, Rich G A & Gregory C R (2000) Osteosarcoma in a California mountain kingsnake (Lampropeltis zonata). In: Proc IVCVM: Diseases of Reptiles and Amphibians.
• Schönbauer M, Loupal G & Schönbauer-Längle A (1982) Osteoid chondrosarcoma in a desert monitor (Varanus griseus). Berliner und Munchener Tierarztliche Wochenschrift 95 (10), 193-194 VetMedResource.

Other sources of information

• Reavill D R (2019) Neoplasia. In: BSAVA Manual of Reptiles. 3rd edn. Eds: Girling S J & Raiti P. BSAVA, UK. pp 397-410.