Archive Case #152: Feline Injection Site Sarcoma

Clinical Clues

1. A cat is presented for a firm mass over the lateral thorax that has enlarged steadily over several weeks.
2. The owner remembers vaccination in the region months earlier.
3. The lump is fixed and extends deep into surrounding tissues.
4. Fine needle aspiration is poorly diagnostic, but the mass behaves aggressively.
5. These tumours are locally invasive and often require wide surgical planning.
6. Injection site sarcoma is an important malignant soft tissue tumour syndrome in cats.

Diagnosis

Feline Injection Site Sarcoma

This case is most consistent with Feline Injection Site Sarcoma because the cat has a deep progressive mass at a prior injection region with aggressive local behaviour. The most important clues are the location and invasive nature, which make a simple post-vaccinal swelling less likely.

Educational Use

Vetdle archive cases are educational veterinary games for diagnostic reasoning practice. They do not provide veterinary advice, diagnosis, treatment, or professional medical guidance.