Case: Bony swelling in dog Flashcards
Tyron is a 7 year old male neutered retired racing greyhound. His relevant history is an old racing injury in his left forelimb (sprain of the radial collateral ligament). He has been coming to see your practice regularly.
Reason for presentation
- Mrs Robinson has brought Tyron to the clinic with a history of 2 weeks progressive right hindlimb swelling and lameness
- She cannot recall any incident in which Tyron may have injured the leg in the last 2 weeks
- The swelling is increasing in size
- Tyron vocalises when the area is touched and is markedly lame but is otherwise well in himself
- In the last week Mrs Robinson treated Tyron with Rimadyl (carprofen) at 1mg/kg SID (treatment left over from his last injury) with no improvement
Physical exam
- On physical examination, you find a 4x2x2xcm firm, haired swelling of the right distal hind limb above the hock
- He is 7/10 lame on the leg and vocalises when the mass is palpated
- The right popliteal lymph node is not enlarged
- No additional abnormalities are noted on a full physical examination
1. Summarise the history and clinical findings for your clinical records as SOAP - just subjective and objective
(soz this so long, just thought we might need a summary slide)
Subjective:
- Progressive right hand lameness and swelling
- Swelling increasing in size
- Vocalisation when touched
- Well in himself
Objective:
- 4x2x2xcm firm, haired swelling of the right distal hind limb above the hock
- He 7/10 lame on the leg and vocalises when the mass is palpated
- The right popliteal lymph node is not enlarged
- No additional abnormalities are noted on a full physical examination
Create a differential diagnosis for this dogs mass
- Osteosarcoma
- Chondrosarcoma
- Multiple Myeloma
- Swollen hock syndrome
- Periostitis
- Abscess
- Arthritis
Make a plan for a step-by step investigation of the mass
- Radiograph
- Biopsy
- Bloods
- Advanced imaging
Are greyhounds a classic breed for an osteosarcoma?
Yes - more common in large/giant/tall breed dogs
Is the hock a typical site for a mass for an osteosarcoma?
The hock is a common site
Common: limbs, skull, ribs and spine
Are the limbs the commonest site for an osteosarcoma? Do osteosarcomas occur anywhere else in the skeleton?
Yes the limbs are the most common. Also found in skull, spine and ribs
Tyson is neutered - is this a risk factor for an osteosarcoma?
Research has found there is a 2 fold increase in incidence of osteosarcoma in neutered animals compared to entire
Plan a diagnostic work-up for Tyron (potential osteosarcoma, bone mass) if money was no object
What would you do if money was no object?
- Radiographs, CT, MRI, bone scintography
- CT is the most accurate technique when intramedullary fibrosis is taken into account
- however, CT overestimates the degree of bone involvement by 27%
- MRI overestimates the degree of bone involvement by 3%
- Bloods and urinalysis –health of the animal and develop anaesthetic protocol
If it is an osteosarcoma on his hock, where do you need to look to check for metastases?
Thoracic and bone
Other metastatic sites include regional and distant LNs, kidneys, spleens, myocardium, diaphragm, mediastinum, SC, SI, gingiva and subcutaneous tissues
Describe these radiographic appearances of the bone mass on Tyrons hock
Irregular localised lesion to the distal aspect of the femus. Poor demarcated borders with a mixed radiopacity
These are views of Tyrons thorax:
- What are you looking for?
- How could they be improved?
- Are there any other imaging modalities to look for thoracic pathology?
- Metastasis
- Inspiratory views
- CT
What are some possible differential diagnoses for a bony mass?
- Osteosarcoma
- Chondrosarcoma
- Fibrosarcoma
Less likely:
- Haematoma
- Granuloma
- Cyst
- Abscess
- Osteoarthritis
What is the signalment of a canine osteosarcoma?
- Most common bone tumour of dogs
- Typically large-giant breed dogs e.g. rottweilier, Doberman, Irish Wolfhound, Great Dane, Golden Retriever, GSD
- Longer limbs increase risk within breed
- Neutering seems to increase risk
- Common site: metaphyseal bone:
- FL: distal radius > proximal humerus - AWAY FROM ELBOW
- HL: distal femur > proximal tibia - TOWARDS THE KNEE
How can you confirm the diagnosis of an osteosarcoma?
Bone biopsy to look at cells under microscope
What is the prognosis of canine osteosarcoma?
Despite all our best efforts, dogs with appendicular (long bone) OSA will almost certainly be lost to the disease, either from the primary tumour (the bone) causing uncontrollable pain, or the secondary tumours (the metastases) affecting the quality of life of the dog. The commonest site of spread is the lungs, and advanced disease here most commonly causes weight loss and weakness (cachexia), not breathing problems as you might expect.
