Abstract
Background:
Feline lymphoma is often a fatal disease and the possibility of achieving a cure with chemotherapy is questionable. A diagnosis of FIP was historically associated with a poor prognosis and high mortality, but with the newly available treatment, remission is possible. Long-term follow-up data on treated cases remain limited.

Case description:
A 3.9-year-old neutered male cat was presented with hyporexia and lethargy lasting several days. An abdominal mass was palpated on clinical examination and confirmed to be a renal mass on a computed tomography angiography (CTA) scan. Ultrasound-guided fine needle aspirates were performed, and cytological evaluation revealed a large-cell renal lymphoma. A modified COP protocol with the addition of vinblastine (COVP protocol) was started, resulting in a complete response. Twenty weeks after starting chemotherapy, the cat developed anorexia, fever, and pleural effusion. Feline infectious peritonitis (FIP) was diagnosed based on a positive RT RNA PCR test from the pleural effusion. Subcutaneous GS441524 administration led to FIP resolution.

Conclusion:
The cat did not receive any further treatment for both FIP and lymphoma and is still alive and well, almost 5 years after the diagnosis. To the author's knowledge, this is the first case of renal lymphoma in a cat that subsequently developed FIP. Further studies on the potential correlation of lymphoma, chemotherapy and FIP are needed.

Key words: CHOP protocol; FIP; Remdesivir; Renal lymphoma.