DM2 Pt5-3 Feline Injection Site Sarcoma (FISS)

Question 1

What were feline injection site sarcomas (FISS) originally called?

Answer 1

They were originally called “vaccine site-associated sarcomas.”

Question 2

When were feline injection site sarcomas first reported, and which vaccine was initially linked?

Answer 2

They were first reported in 1991 and linked to rabies vaccination.

Question 3

Why were FISS renamed from vaccine site-associated sarcomas?

Answer 3

Because they can occur after any injection, not just vaccines, including antibiotics and corticosteroids.

Question 4

What is one significant risk factor for developing FISS?

Answer 4

The number of injections at a site; 3-4 vaccinations in the interscapular region doubles the risk.

Question 5

How does the temperature of a vaccine affect the risk of FISS?

Answer 5

Administration of cold vaccines increases the risk compared to room temperature vaccines.

Question 6

Does the brand or manufacturer of the vaccine increase the risk of FISS?

Answer 6

No, vaccine brand or manufacturer is not associated with increased risk.

Question 7

Does re-using disposable syringes increase the risk of FISS?

Answer 7

No, re-using disposable syringes is not associated with increased risk.

Question 8

Does shaking multidose vials or massaging the area post-vaccination increase the risk?

Answer 8

No, neither shaking vials nor massaging the area increases the risk of FISS.

Question 9

What is the primary treatment challenge for interscapular FISS?

Answer 9

Interscapular FISS are challenging to treat due to their aggressive nature.

Question 10

What diagnostic tests are recommended for assessing FISS?

Answer 10

Full haematology, biochemistry, FeLV/FIV status, urinalysis, and biopsy are recommended. Cytology is not reliable.

Question 11

How long should inflammatory reactions post-injection resolve?

Answer 11

Inflammatory reactions should resolve in 6–8 weeks.

Question 12

What is required to definitively diagnose FISS?

Answer 12

A biopsy is required to definitively diagnose FISS.

Question 13

What imaging techniques are recommended for staging FISS?

Answer 13

Thoracic CT or three-view inflated thoracic radiography to check for metastases.

Question 14

Where does FISS most commonly metastasize?

Answer 14

The most common site for metastasis is the lungs, but it can also spread to liver, lymph nodes, and subcutaneous tissue.

Question 15

What are the recommended surgical margins for FISS excision?

Answer 15

3–5 cm lateral margins with two muscle layers or bone as the deep margin.

Question 16

Why is the first surgery critical in treating FISS?

Answer 16

The first surgery is the most effective for curative treatment.

Question 17

What complications may occur after radical surgery for FISS?

Answer 17

Complications include wound dehiscence and seroma.

Question 18

What are the key components of postoperative care after radical FISS surgery?

Answer 18

Support dressing, multimodal analgesia (opiates, NSAIDs, local anesthesia), suction drains, and assisted feeding.

Question 19

What are the factors that influence prognosis in FISS treatment?

Answer 19

Factors include location of FISS, clean vs dirty margins, number of surgeries, surgeon experience, tumor grade, and metastasis development.

Question 20

Why is recurrence common even in cases with clean surgical margins?

Answer 20

Due to the infiltrative nature of the tumor and potential ongoing inflammation leading to further tumorigenesis.

Question 21

What is the tumor recurrence rate in FISS cases with histopathological clean margins?

Answer 21

Recurrence rates in cases with clean margins range from 14–50%.

Question 22

When is radiotherapy used in FISS treatment?

Answer 22

Radiotherapy is used as an adjuvant therapy postoperatively or preoperatively to treat microscopic disease.

Question 23

Why might tumor cells become more resistant to radiotherapy after surgery?

Answer 23

Surgery can damage blood supply to tumor cells, making them more radioresistant.

Question 24

Is chemotherapy proven to be effective in treating FISS?

Answer 24

The efficacy of chemotherapy is unproven, though it is used due to the high metastatic rate of FISS.

Question 25

What is the recommended treatment for small FISS tumors?

Answer 25

Wide excision after incisional biopsy, with or without radiotherapy.

Question 26

What is the recommended treatment for larger FISS tumors?

Answer 26

A combination of surgery, radiotherapy, and possibly chemotherapy.

Question 27

What task force was created in response to the appearance of FISS?

Answer 27

The Vaccine-Associated Feline Sarcoma Task Force (VAFSTF) in North America, 1996.

Question 28

What region do AAFP and WSAVA recommend avoiding for vaccine administration?

Answer 28

The interscapular region should not be used for vaccinations.

Question 29

Where does the AAFP recommend vaccines be administered in cats?

Answer 29

The distal limbs.

Question 30

Where does the WSAVA recommend vaccines be administered in cats?

Answer 30

The lateral abdomen or thorax, changing the site of administration each time.

Question 31

What is the recommended vaccination frequency for FHV, FCV, and FPV according to WSAVA and AAFP?

Answer 31

Every 3 years, although many practitioners in the UK still vaccinate annually.

Question 32

How often is FeLV vaccination recommended for older cats according to the ABCD?

Answer 32

Every 2–3 years, depending on risk.

Question 33

Why is vaccination at the stifle level in the hind limb preferred over the interscapular region?

Answer 33

It allows good surgical margins with amputation if an injection site-associated sarcoma develops.

Question 34

What drugs, besides vaccines, have been associated with injection site-associated sarcomas?

Answer 34

Long-acting corticosteroids and long-acting penicillins.

Question 35

What types of injections besides vaccines have been linked to FISS?

Answer 35

Long-acting antibiotics and steroids.

Question 36

What is the most important component of treatment for FISS to ensure prolonged disease-free intervals?

Answer 36

Radical surgical excision.

Question 37

When should adjunctive radiotherapy and chemotherapy be considered for FISS treatment?

Answer 37

For large grade 3 tumors where surgery alone is unlikely to be curative.