My 11 year old cat has a lump on her hind leg which I believe was caused by a knock to the area after being chased by a neighbours dog that entered my garden, causing my cat to run under the house, I heard the scuffle & not long after she developed this lump, which my vet diagnosed as a seroma, they took a biopsy which was inconclusive. The assesment states Distal left hindlimb mass 1.5 cm tumour (bening or neoplastic) with enlargement due to seroma. She shows no signs of pain in area only when touched, walks fine and is acting perfectly normal. Vet recommended surgical removal costing $1800 .Any advice would be greatly appreciated. I include an image of actual lump