Feline Medicine Q&A 17

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A cat that was vaccinated 2 months ago is returned because the owner can feel a 2 cm diameter lump at the site of vaccination.

Question	Answer		Article
What are the possible causes of this lump?	The lump could be inflammatory, for example, a granuloma caused by an inflammatory reaction to the vaccine constituents. The main alternative concern would be that this represents a vaccine site-associated sarcoma. Other causes, unrelated to vaccination, would include a cat bite abscess.		Link to Article
What is the most appropriate diagnostic plan?	One option would be to monitor the lump for a further month by which time most inflammatory reactions will have disappeared or reduced in size. However, at 2 months post-injection, because of the concern over potential vaccine site-associated sarcoma, an incisional or needle biopsy should ideally be performed (either of these would be far preferable to a fine needle aspirate, results of which would be more difficult to interpret). The lump should not be completely excised as this usually makes further radical surgery (such as that required for treatment of vaccine site-associated sarcoma) much more difficult and less successful.		Link to Article