Published evidence supports the notion that MSLN- and CA125-specific immune responses are beneficial [32–34] and that promising preclinical and ongoing early-phase clinical studies have demonstrated that MSLN and CA125 may be effective cancer antigens to target with immunotherapy for solid tumors [35–37]; however, the frequency and distribution of CA125 and MSLN co-expression in MPM have not been previously studied. The gene discussed is MSLN; the disease is cancer.