MYCN and retinoblastoma: Furthermore, RNAseq data from five Rb tumours suggested that increased N-MYC expression is a common feature of tumours with 2 or 3 copies (11- to 21-fold), compared to normal retina, and demonstrated a dramatic increase in expression in the 185-fold MYCN amplified tumour, thus suggesting that MYCN expression may be increased in all Rb tumours, further implicating the role of N-MYC in the development of Rb tumours in general.