Treatment of Feline Lung–Digit Syndrome with Toceranib Phosphate: Prolonged Survival and Novel Metastatic Findings

Feline pulmonary carcinomas are rare and often carry a poor prognosis, particularly when associated with feline lung-digit syndrome. We report a cat with primary pulmonary carcinoma and extensive metastases-including digits, pleura, mandible, scapula, spleen, skeletal muscle, and distant lymph nodes-supporting the broader "MODAL syndrome" concept. Palliative therapy with toceranib phosphate and meloxicam achieved prolonged survival and excellent quality of life, with no adverse effects despite dose escalation. Rapid progression after discontinuation suggests a role for toceranib in delaying tumour growth. Immunohistochemistry revealed c-kit expression in one metastatic lesion but not in the primary tumour or most metastases, highlighting intratumoral heterogeneity and the complexity of targeted therapy. The observed benefit likely reflects toceranib's multi-target activity (VEGFR2, PDGFR), impacting angiogenesis and tumour progression. This case represents the first report of toceranib phosphate use in feline pulmonary carcinoma and underscores its potential as a palliative option.