MAPK1 and histiocytic sarcoma: In the field of tumor biology, spontaneous neoplasms in companion animals are recognized as appropriate models for the investigation of human tumors, especially in rare neoplasms where it is difficult to gain deeper mechanistic insights and develop therapeutic options [46,47,49,50]. Nevertheless, the molecular features of canine histiocytic sarcoma, as determined by gene expression analysis, indicate an activation of the ERK and Akt [51] as well as the NF-κB pathways [52,53].