To investigate zRMS growth and progression in single and double pax3 mutants, we compared zRMS detected in pax3a:EGFP, pax3a−/−;pax3a:EGFP, pax3b−/−;pax3a:EGFP and pax3a−/−;pax3b−/−;pax3a:EGFP zebrafish lines and embryos were observed daily using a fluorescent dissecting scope for putative tumour growth. Here, PAX3 is linked to neoplasm.