Injection Site Sarcoma

Question 1

How do injection site sarcomas typically behave?

Answer 1

extremely locally invasive with tendrils or fingerlike projections

• metastatic rate of 20-25%

Question 2

What is thought to cause injection site sarcomas? What vaccines and other injections are thought to have increased rates?

Answer 2

inflammation associated with injections, particularly concerning the adjuvant

• VACCINES - rabies, FeLV
• INJECTIONS - Lufenuron, Penicillin, microchips

Question 3

What 3 diagnostics are recommended for possible cases of injection site sarcomas?

Answer 3

1. biopsy - more accurate than FNA; necrosis, inflammation with lymphocytes and macrophages (containing adjuvant), and more mitotic figures
2. thoracic radiographs - assess for pulmonary metastasis
3. CT/MRI - assess invasiveness for surgical planning

Question 4

How are injection site sarcomas treated?

Answer 4

radical excision with 3-5 cm lateral margins and 2 fascial planes deep

• amputation if on a limb
• body wall resection with hemipelvectomy for proximal pelvic limbs
• dorsal spinous process removal and partial scapulectomies if interscapular

Question 5

What is the recurrence of injection site based on treatment?

Answer 5

• conservative surgeries = 2 months
• radical surgeries done by referral surgeries = 9 months
• clean surgical margins / complete histopathology = 16 months

Question 6

What adjuvant therapy is recommended with injection site sarcoma treatment?

Answer 6

radiation –> prolongs recurrence if margins are narrow or incomplete on histopathology

Question 7

What chemotherapy is recommended for cats with injection site sarcomas?

Answer 7

adriamycin (Doxorubicin) –> 50% response rate

• unclear if it prolongs survival time
• more helpful in cats with microscopic metastatic disease or those with incomplete surgical excision

Question 8

How can injection site sarcomas be prevented?

Answer 8

• only vaccinate for diseases that a cat may be exposed to or if it is required by law
• vaccinate as distally on the limb as possible so an amputation is possible

Question 9

How should vaccines be standardized to keep track of vaccines that cause injection site sarcomas?

Answer 9

• rabies = RH
• FeLV = LH
• feline rhinotracheitis and panleukopenia (FVRCP) = RF

give as distally as possible!!