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Oncology blog

Four thoughts on investigating an osteolytic bone lesion

19th October 2017

1. Do I need to take a bone biopsy?

Why not do an FNA? Fine needle aspiration of bone lesions can be an effective way of demonstrating cancer cells and this is all the information you need to decide the first step in treatment (surgery). The precise tumour type (eg chondrosarcoma versus osteosarcoma) is usually less important at this stage, but knowing whether the lesion is inflammatory or neoplastic is key.

To get a good cell harvest with an FNA of a bone you need a very different aspirate technique to that for a lymph node however. Try the following and see what you think:

  • Use a long 21g needle with 10ml syringe attached
  • Insert into the middle of the lesion and apply 5-10mls negative pressure.
  • Move the needle back and fore / re-angle it several times, keeping negative pressure applied.
  • Remove and
  • You will get a lot of blood with this method, but also a decent yield of neoplastic cells, so make at least 10 slides, and stain 1-2 in-house and check to make sure you have caught cells other than blood / inflammation before sending them off.
  • This technique is cheaper, and quicker than a bone biopsy, and avoids the risk of pathologic fracture!(Fine needle aspirate cytology showing a malignant population of mesenchymal cells in a multilobular osteochondrosarcoma at the back of a dog’s skull).

2. If the radiologic findings convincingly demonstrate a bone tumour, isn’t it a waste of the client’s money to pursue a diagnosis before amputation?

The successful treatment of most osteolytic cancers will hinge around local control of the tumour, which in many cases will involve limb amputation. Nevertheless histiocytic sarcoma is a notable exception where coarsely-fractionated radiation therapy produces great results, returning most cases rapidly to full weight-bearing. The dog’s breed and the anatomic location of the lesion may affect the suspicion of this particular malignancy versus osteosarcoma. Cytology should be adequate for diagnosis of a histiocytic sarcoma (or even rarer bone tumours for example lymphoma or plasma cell tumours which can be treated medically).(Proximal humeral osteosarcoma)

3. Do I really need to x-ray the chest?

Although metastasis at the time of osteosarcoma diagnosis is uncommon (less than 20%), the presence of gross pulmonary metastasis will significantly diminish the prognosis for osteosarcoma from approximately 1 year to approximately 3 months. The client may find this information useful in deciding whether to proceed with surgery and chemotherapy.

(Lateral thoracic radiograph showing pulmonary metastasis)

4. Should the dog have an orthopaedic assessment before the amputation?

In most cases, dogs will have been effectively 3-legged for the last few weeks due to non-weight-bearing lameness, so the ability to cope on 3 legs will have already been demonstrated. However, it is always prudent to consider the orthopaedic function of the remaining limbs before an irreversible amputation surgery, and in these increasingly-litigious times we should document that we have done this. Particularly where chronic orthopaedic disease exists, or is suspected, assessment from by an orthopaedic surgeon may be very helpful.

 

If you would like further information or advice please feel free to contact the Highcroft Oncology Service on 01274 838473.

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