The main purposes of this study were to assess the expression of PD‐L1, PD‐1 and CTLA‐4 in canine OM by in situ hybridization (ISH), to analyse the spatial distribution of these molecules within tumour cells and the TME, providing insights into immunosuppressive interactions, and to evaluate potential correlations with histological parameters and disease outcome. This evidence concerns the gene PDCD1 and neoplasm.