Primary lung cancer in cats is most commonly an adenocarcinoma arising from the cells lining the airways or air sacs. A distinctive feature of feline lung cancer is its high rate of metastasis at the time of diagnosis — a high proportion of cats already have evidence of spread at the time of diagnosis. A particularly unusual metastatic pattern is the 'lung-digit syndrome,' in which the cancer spreads to the toes, causing swelling of one or more digits — sometimes the toe swelling is actually noticed before the lung tumour is discovered. Cats with solitary lung masses that have not yet spread can benefit from surgical lung lobectomy, but the high rate of advanced disease at diagnosis means that many cats are not surgical candidates. The disease mainly affects older cats, and symptoms include coughing, difficulty breathing, and weight loss.