NF1 and neoplasm: Histopathologically, the tumor masses that developed in MYCN transgenic fish with nf1 mutations consisted of small, undifferentiated tumor cells with distinct single nucleoli (Figure 2B), which were diagnostic of neuroblastoma and indistinguishable from the tumors that develop in MYCN transgenic zebrafish with wild-type nf1 alleles (Zhu et al., 2012).