First description of oesophageal melanoma in a cat and palliative treatment by endoscopic argon plasma coagulation laser.

Case summary: An 11-year-old castrated male domestic shorthair cat presented with chronic regurgitation and weight loss. Despite a 2-month history of weight loss, regurgitation intensified over 4 weeks, occurring with every food intake, even on a semi-liquid diet. Physical examination revealed thinness and dehydration, and a focal oval mass was noted in the middle mediastinum on thoracic radiography. Oesophagoscopy identified a 6 cm neoformation almost completely obstructing the oesophageal lumen. Biopsies were taken and histopathology, positivity to melanoma triple cocktail and PNL-2 by immunohistochemistry led to the diagnosis of melanocytic neoplasm. Palliative debulking with argon plasma coagulation (APC) was performed, significantly improving the cat's quality of life for 2 months. The cat survived for 107 days after diagnosis.

Relevance and novel information: This case report describes the first report of melanocytic neoplasia originating from the oesophageal mucosa in a cat. In cats, melanomas outside the eyes are exceedingly rare and oesophageal neoplasms are exceptionally rare in veterinary medicine, particularly melanomas. The diagnosis relied on positive immunohistochemistry markers aligning with previous research. Treatment with APC emerged as a novel, potentially palliative approach, successfully alleviating regurgitation for 3 months. This underscores APC's potential in feline oesophageal neoplasia palliative care, which deserves further investigation in a broader feline cohort to confirm its efficacy. Overall, this report provides valuable insights into the diagnosis and treatment of oesophageal melanoma in cats.