Dog lump head

Hi I have a quick question my dog has a lump on her head that has gotten a little bigger. She's had antibiotics and they did nothing so doubt it's an access. On taking her back to the vet he said it was a soft lump he put in a needle to drain it and said green mucusy stuff was coming out, suggestions were to leave it and keep an eye on it or biopsy. She is 15 years old chihuahua x pomeranian... I'm not concerned this is anything bad as she is eating and happy to go for walks etc plus a tumour is a solid mass rather than mucus I believe? Any advice on what to do please

Hello - and first of all, I'm afraid that I have drained green sticky liquids out of tumours, bacteria-filled abscesses and sterile absesses alike, and I don't think you can be so sure that this is not anything bad on the information that you have given me.  Obviously, your vet will have more context than me.  They will know, for example, whether that lump is mostly fluid or tissue or, indeed, bone.  They have not drawn away pure blood or clear fluid, which may have been two other possibilities.  I wonder whether they think that a fine needle aspirate is a good idea, where they take a small sample of the fluid and the surface cells from the lump, put them onto a slide and look for bacteria, cancer, or inflammatory cells.  Pathology labs can offer a service to look at complex cases if the slides and a history are sent to them.  If the bone may be involved, then radiography could be useful. I have always found it helpful to speak to my local lab pathologists about such cases, because they can often advise me as to how best to sample such a lump in order to get an efficient result.  Once your vet has an idea as to what the lump is, they will be well placed to comment on the things that you most want to know; the severity, treatment and prognosis.  Please will you let us know what you find out?  Wishing you and this beautiful, wizened old lady all the best of results.