Hello, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
I am glad to see you have been vigilant with this wee one and have noted this lump's presence. When we see a lump appear on our hedgies, there are a range of potential causes that we have to consider and we always do want to take a proactive stance with them. Specifically, we can see firm lumps of this nature with cysts, abscesses, lipomas, a benign growth, or even a nasty cancer. And I must warn you that this is a species that is very prone to cancers (hence why we always want to act quickly with these wee ones)
As well, as I am sure you can appreciate, the gross appearance of the mass will not give us much hint to the nature of the mass (cancers are too sneaky for that). Though from your mention of the lump's mobility, we can assume that it is only associated with the upper levels of tissue (skin, muscle) and not involved with an internal structure.And while the crusty top could be a hint that this is a walled off bacterial infection, we have to appreciate that it may just be crusty due to secondary skin based infection (which arises if they rub the area or even if the mass stretches the skin a bit too much during growth) arising from any of the aforementioned differentials.
In this situation, the best course of action, would be to have this checked by his vet sooner rather then later. Ideally, we'd want to have his vet evaluate the mass via fine needle aspiration (FNA). This is where the vet uses a needle to harvest cells from the mass. If clear fluid is removed, then a cyst is likely (which can be removed or monitored since its not a sinister issue for them). If they remove pus, then its a sign of infection (which can be treated with antibiotics). If fat cells are present, then again this is something that can be removed surgically but often does not need to be.
Otherwise, if these characteristic findings are not seen, then the sample's cells are stained to allow the vet to identify the nature of the mass. And once they know what it is, they can advise you on what needs to be done regarding the mass. As well, at the same time, the vet will be able to examine your wee hedgehog and determine if there are any other issues afoot that might hint whether then mass is causing trouble for the body (ie harsh lungs sounds suggesting spread to the lungs or a any further internal masses, etc).
Overall, it is not possible to determine what type of growth this is without having a peek at what is inside the mass. We often find benign growths that look sinister and terrible and we can also find nasty cancers that appear quite docile. Therefore, I would strongly advise that it would be ideal to have his vet check this lump and potentially take a sample of the mass by FNA (especially since cancer is so common to this species). Because the the sooner you know the identity of this abnormal growth, the sooner you will know if it is a worry and will be able to effectively address it for your wee one.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
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