Feline lung-digit syndrome: A differential diagnosis for shifting, waxing and waning lameness in a cat.

The clinical presentation, cytologic findings, radiographic findings, and postmortem assessment of a cat with primary pulmonary adenocarcinoma with multiple digital metastasis are described. An unusual shifting, waxing and waning pattern of lameness, suspected to be an early manifestation of digital metastasis before any gross lesions were visible, was documented. Initial cytologic finding of a lung nodule was equivocal for diagnosis of neoplasia despite being strongly suspicious. Palliative management was short-lived, with rapid progression culminating in widespread metastasis to multiple digits, muscles, and other organs. The diagnosis of pulmonary adenocarcinoma was confirmed via necropsy and histopathology. Key clinical message: This case report highlights that feline lung-digit syndrome is an important differential diagnosis for an acute, waxing and waning, shifting leg lameness in an older cat. This pattern of lameness should raise the index of suspicion for an underlying primary lung neoplasm, and thoracic imaging (radiographs) should be considered.