IHC uses primary antibodies to highlight any type of antigen expressed by normal host cells, viruses, bacteria and tumoural cells, and such versatility made IHC an invaluable tool for research focussing at the same time on protein expression and morphology. While IHC more deep technical aspects are beyond the scope of this manuscript and will therefore not be discussed (for additional data, see Ramos-Vara & Miller, 2014), we will briefly discuss the importance of IHC in equine diagnostic pathology, condensed in a few paragraphs.All the IHC markers mentioned in the present study refer to IHC performed on formalin-fixed paraffin-embedded (FFPE) tissue, as this represents the most diffuse IHC used in veterinary pathology.