Feline Injection Site Sarcomas

Presenters – Rob Adams BVM&S MRCVS, Resident in Small Animal Surgery, Davies Veterinary Specialists, covering the pathogenesis and diagnosis of FISS; and Rachel Hattersley BVetMed(Hons) CertSAS DipECVS MRCVS European Specialist in Small Animal Surgery, Davies Veterinary Specialists, discussing treatment options

If you want to learn as much as you can about feline injections site sarcomas (FISS) in the space of an hour and from the comfort of your own home then last week’s veterinary webinar organised by ‘The Webinar Vet’ makes for perfect watching. We were privileged to have two speakers leading this webinar with Rob Adams BVM&S MRCVS covering the pathogenesis and diagnosis of FISS, and Rachel Hattersley (European specialist in small animal surgery) discussing treatment options.

This veterinary webinar delivered a plethora of information and from this came some key take home messages. Rob explained that post vaccination ‘lumps’ are relatively common and it is useful for us to know when to intervene. Three criteria set for intervention include a post vaccination lump which has been present for longer than three months, and/or a lump which is larger than 2cms in size, and/or a lump continues to increase in size at least one month after vaccination.

When intervention is necessary Rob advises against cytology to make a diagnosis as often these tumours do not exfoliate well and a negative cytology result does not rule out FISS. A narrow and deep incisional wedge biopsy should be performed and Rob strongly advised against performing an excisional biopsy as these cases will often require further more aggressive surgery which generally means these cases won’t go on to do as well.

Rachel discussed treatment of FISS with surgical excision being the primary option. She stated that ‘the first surgery is the best surgery’ and margins of at least 4-5cms should be achieved whilst resecting two fascial planes deep or bone if present. Studies have shown that margins of this depth will lead to a 14% recurrence rate where as other studies have shown a recurrence rate of 39% when resection was only one fascial plane deep. Rachel also emphasized that the success of these surgeries is greater when performed by experienced surgeons.

She went on to discuss surgery in greater depth also covering analgesia including the use of fenestrated catheters to administer bupivicaine direct to the surgical site. Adjunctive therapies including chemotherapy and radiotherapy were also discussed.

There was however one ‘fly in the ointment’ when it comes to managing these cases with optimum success. Despite knowing there are better cure rates with distal limb and tail feline sarcomas as full amputation can be performed and despite the Vaccine Associated Feline Sarcoma Task Force advising the use of a rotating limb vaccination protocol, 95% of vets in the UK still vaccinate in the interscapular area (myself included).

To defend myself I would say that vaccinating in the distal limb or tail of the cat would not always be easily achieved especially in the fractious cat. However Rob explained that studies have shown vaccinations at these sites are well tolerated by cats with, somewhat surprisingly, distal tail vaccination being best tolerated. So with FISS being such a devastating condition I wander why we have not embraced distal limb vaccination. I know some clients would find it a little ‘odd’ and maybe we just don’t see enough cases of FISS to want to ‘rock the boat’ and alter a long standing and trusted technique.  It would certainly be an interesting debate for the profession to have and a discussion hosted by ‘The Webinar Vet’ could be a great place to start.

The Stethoscope (MRCVS)

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