Parkinson’s disease is a degenerative disease of the central nervous system, and studies have shown that patients with Parkinson’s disease are less likely to develop tumors overall and have a different tumor profile than the general population. Jansson’s study showed that the incidence of tumors in 406 Parkinson’s disease patients was only 1/3 that of the general population. Benign and malignant thyroid tumors were more prevalent in Parkinson’s disease patients. Another population-based study of tumor mortality in Parkinson’s disease patients (10322) conducted in Vanacore showed that a total of 448 Parkinson’s disease patients died from tumors between 1987 and 1994, a significantly lower rate than the comparator in this population. Because smoking is a protective factor for Parkinson’s disease but a risk factor for tumor development, the group further refined the association between the type of tumor and Parkinson’s disease and found that both smoking-related tumors (e.g., lung, larynx, bladder) and smoking-unrelated tumors had significantly lower rates than controls. However, the possible mechanisms for the increased risk of malignant melanoma, other skin cancers, and breast cancer are unclear.