To detect the presence of specific tumour markers within the xenografts, we performed the immunohistochemical detection of PRIM1 (DNA primase polypeptide 1), which is known to be overexpressed in OS, H3F3A-G34W, which detects a mutation within the histone H3.3 that is characteristic for GCTB, and Collagen Type II, which is highly expressed in cartilage tissue and CS. The gene discussed is PRIM1; the disease is neoplasm.