large lump on neck

Question
I have a male guinea who has just turned 4 and has over the past 2 weeks developed a large lump/swelling under his neck.  It seems to be getting worse and now effecting his eye (his left eye seems to be looking smaller than the right.  He has also become very boney although he is gaining weight.  We have had him to the vet but no joy. Any ideas? I just dont want to be causing him to suffer or not not to be helping him if he can. He has already had a course of anti biotics which havent helped at all.

Answer
Hi
feel the swelling, does it move with the skin or does it feel like a solid mass that is stuck to the skeleton?
If it feels loose it could be a cyst and may need lancing.
If it is a tumour or something else bad then it will not be as freely moving and your vet may need to do a biopsy.
I would take him back to the vets and ask him to put a needle into it to see if any fluid can be drawn off.
xxx