Step 4: Imaging

Objective :

Recognize features of an abnormal X-ray

Tip 1

This line across the tibia is the normal growth plate. It somewhat resists tumour spread, depending on the pathology, and you can see this tumour has not grown past it.

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Tip 2

The tumour is extending beyond the bone into the soft tissues to produce this soft tissue mass. This is a sign of an aggressive tumour.

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Tip 3

The tumour is radiodense and shows up as this white area in the bone. The density is due to the abnormal bone (‘malignant osteoid’) being laid down by the tumour cells.

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Tip 1

A Codman’s Triangle is produced by the periosteum as it is lifted by the tumour. It is a sign of an aggressive tumour. It isn’t always seen, but here it is the inverted triangle between the new and old bone on the medial edge of the tibia.

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Tip 1

The edge, or margin, of the tumour can give a lot of information about the tumour. This margin is very poorly defined, indicating a rapidly growing tumour.

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What is the most likely diagnosis?

Osteosarcoma

Tip 6

Yes. This X-ray has many hallmarks of Osteosarcoma : New bone formation, a Codman’s triangle, a soft tissue mass and a poorly defined margin.

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Infection

Tip 7

This is possible, but not the most likely. Infection can mimic malignant tumours, so it will need to be carefully ruled out. Blood tests such as a CBC and CRP can help.

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Rheumatoid Arthritis

Tip 8

No. This would have shown a normal X-ray or possible changes affecting the joint such as peri-articular erosions.

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Fracture

Tip 9

There are no signs of fracture on this X-ray.

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More Info Next Step

As this boy had prolonged, unexplained bone or joint pain an X-ray was ordered. His history was also atypical for traumatic or inflammatory causes. An X-ray is a simple and cheap test that can exclude a lot of serious pathology.