Mesotheliomas in individuals younger than 55 years, with a M:F ratio close to 1:1, and equally distributed between pleura and peritoneum, are instead often associated with environmental exposure to carcinogenic fibers present in the natural environment—which cause exposure since birth, or they develop in individuals carrying germline mutations of BAP1 or of other tumor suppressors genes [6, 9]. The gene discussed is BAP1; the disease is mesothelioma.