The involvement of neural crest derivatives in SS is further supported by strong expression of genes encoding the (neuro)cartilage marker collagen IX, neurofilament heavy polypeptide NEFH involved in axonal scaffolding and radial growth, endothelin 3 required for melanocyte and enteric neuron differentiation, and the chondrogenic transcription activator SOX9 [28]. This evidence concerns the gene SOX9 and synovial sarcoma.