You have asked…What is the ideal way to identify and approach feline injection-site sarcoma?
Feline injection-site sarcomas (ISSs) primarily arise at sites of vaccination (called vaccine-associated sarcomas) but have also been associated with administration of injectable lufenuron, microchips, and long-acting antibiotics or corticosteroids. ISSs have been described at locations where nonabsorbable suture materials have been used. Varying lengths of latency (4 weeks to 10 years) between the inciting event and diagnosis of sarcoma have been reported.1
Examination of an incisional biopsy specimen is recommended for suspected ISS. The specimen should be obtained from an easily excised site without further extension of the surgical field. Excisional biopsy specimens are contraindicated because of increased risk for tumor recurrence and decreased disease-free intervals and survival times.1,2
Fine-needle aspiration and cytology and small trucut biopsy specimens are not recommended for suspected ISS, as the extensive inflammation found in these tumors can lead to a misdiagnosis of granuloma. Most ISSs are fibrosarcomas, but osteosarcomas, chondrosarcomas, malignant fibrous histiocytomas, rhabdomyosarcomas, and undifferentiated sarcomas have also been reported.
After ISS diagnosis is suspected or confirmed, staging should include a minimum database (CBC, serum biochemical panel, urinalysis) and 3-view thoracic radiography. Abdominal ultrasonography should also be considered for caudally located tumors.1