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Why you can’t diagnose a lesion based on a single CT slice

I was just commenting on a lesion posted on twitter and I thought this would make a good blog post. @Vitaltooth posted this image, a single slice from a CT scan.

54/M c.o of Swelling in Lft Lower Facial Region since 2 weeks. Axial CT scan of Pt revealed ………

Let’s list what we can tell from this image and then what I would like know but can’t tell because it’s just a single slice.

What I can tell:

It’s a well-defined, hypodense lesion expanding largely lingually, thining and perforating the lingual cortex.

What I would like to see from the CT scan but can’t tell definitively from this one slice:

Is there also thinning, expansion, perforation of the buccal cortex in another slice? Is there a definite sign of cortication anywhere? Are the internal hyperdensities calcifications or are they wispy septae. Does it resorb some of the root? I think so, but can’t say for sure.

Although this slice presumably shows the largest axial dimension of the lesion, you can’t see much or any of the part of the margin that might clue you in to whether or not it is corticated. I would also like to see a thick sagittal slice or the reconstructed pano to get an impression of the margin – whether it is corticated or not.

Anyway, I still bit the bullet and started throwing out possible diagnoses. So I’ll take you through my thought process.

My first, gut impression was aneurysmal bone cyst, but those are rare over 30. Similar to that is a giant cell lesion, since he’s over 50 you have to think Brown’s tumor of hyperparathyroidism if you are thinking giant cell. If we take the hyperdensities to be internal calcifications, CEOT fits the patient demographics. But we could consider the more common epithelial odontogenic tumor – ameloblastoma. Another impression was that of a hemangiom or vascular malformation. If I could tell whether or not it was associated with canal, it would give more or less weight to that diagnosis. Final differential – Ameloblastoma, CEOT, hemangioma, giant cell tumor (check for hyperparathyroidism).

So I hope that shows why you should never do what I did and attempt to diagnose from a single slice. You are limited to a small fraction of the information that is available to you if you have the entire dataset. I still don’t know what the final diagnosis was. When I find out, I’ll come back and update this. We’ll see if I was close at all or if I should have followed more convention wisdom by not attempting to diagnose from a single slice.

7-9-15 Update: This was a hemangioma. My first gut instinct was aneurysmal bone cyst, but that doesn’t really fit here. My second was hemangioma. Should have gone with the gut, thought I still had it third on my list… not bad for a single slice with so many unanswered questions.

Hemangiomas are arguably the lesion we should be most wary about. You may have seen the facebook post going around recently about a patient who died from blood loss when a dentist cut into one of these. They are a benign proliferation of blood vessels and they are very prone to bleed… a lot. Frequently requiring therapeutic embolization by an interventional radiologist.