Lump rapidly growing

URGENT QUESTION! Hello, my dog has this lump on his paw which has been growing bigger as time goes on. Could someone identify what this lump could be from these photos or what type of a tumour it could be? Thank you so much

Hello!  This is a common question, and because of that there are several articles on our blog about it.  I'm sure that I wrote one a few years ago and others have done since - search 'lump' in the blog for more information. In short, it is very difficult to tell the nature of a lump from the outside and so sampling or radiography are often required.  Different sorts of sample turn up different types of information, but are differently invasive (eg a fine needle aspirate is near-painless and quick, but only yields a few scattered cells and can miss things; removing a whole lump can be invasive, but gives the best understanding of the layout of cells in the lesion; biopsies stand in between). Lumps that are not cancer can be inflammation, perhaps a consequence of skin disease or a reaction to a foreign body or trauma. Happy reading - and I'm here for any further questions.  

To enlarge on this, there is a massive range of possible diagnoses for a lump between the toes, ranging from skin disease such as demodex mite infestation, wasp sting, autoimmune or allergic skin disease (very common, with swelling of skin secondary to licking or to infection as a result of having being licked, for example), or possibly a lump from licking due to arthritic pain, or underlying bone cancer, or else a foreign body or even a fracture.  Another cause might be benign or aggressive skin cancer.  Your vet may have to do tests to find out which answer is appropriate in this particular case and may start by ruling out the easiest, or the most likely or most worrying possibilities, depending on their findings.  Biopsy, trial treatments or radiography may be proposed.   If just one area is being licked, local changes may be suspected; if it is widespread across the digits / feet, skin allergy and secondary problems may be one of the likely possibilities.   Best of luck and please let us know how you get on.