PDGFRB and neoplasm: Interestingly, stromal SPARC expression correlated negatively with the MPM tumor cell marker staining (combination of CK5, calretinin, and CK5/6) (Spearman's rho: −0.432; p = 0.001) and positively with tumor cell PDGFRB expression (Spearman's rho: 0.314; p = 0.008).