PDGFRA and gastrointestinal stromal tumor: In order to verify the occurrence of PDGFRA expression in our series and assess the possible mRNA expression of ISLR/Meflin and PDGFRA, we used PDGFRA immunostaining and, in the absence of a commercially available Meflin antibody working on formalin fixed paraffin embedded (FFPE) tissue, carried out ISH against PDGFRA and ISLR/Meflin using a PDGFRA-positive gastrointestinal stromal tumor (GIST) as an in-built control (Figure 6).