EXT2 and chondrogenic neoplasm: Since the biological nature of benign cartilage tumours is still debating, we will have to elucidate this aspect by performing a preclinical 99mTc-NTP 15-5 imaging study of rodent models of enchondroma, (such as mutant mice for hedgehog signalling pathways or Ext1/Ext2 exostosin encoding gene) in parallel to the biological characterization of PG of tissue [23–25].