PRRX1 and malignant peripheral nerve sheath tumor: Upregulation of developmental genes like BMP7, SMO, VANGL2, SFRP1, PRRX1, MDK, OLFM, IGFBP3, IGFBP5 and TGFBR3 in the fibrosarcoma samples suggests similarity to SS, GIST, myxoid/round-cell liposarcoma and MPNST explaining its classification within subcluster S in Figure 1 [see Additional files 19 and 20].