Although it's uncommon, hypertrophic osteoarthropahy, or HPOA, is an odd and therefore memorable syndrome that can be a side effect of lung cancer. It features an abnormal proliferation of skin and bone tissue, primarily in the hands and feet. Patients can develop clubbing, which is most commonly associated with NSCLC (up to 1/3 of patients) more than SCLC (only about 5%), and adenocarcinoma in particular. Here's what it looks like: