MDM2 and neoplasm: PDGFRA IHC using an N-terminal antibody (aa 32-324, absent in MDM2::PDGFRA) highlighted the presence of two clones of tumor cells (Fig. 2B, PDGFRA): one with strong (3+) PDGFRA expression, likely derived from wild-type PDGFRA and a second lacking N-terminal staining – colocalizing with region of reduced MDM2 IHC (epitope aa 26-169), consistent with MDM2::PDGFRA expression.