These new neurons had developed from neural progenitor cells, a type of undifferentiated neuron akin to a stem cell, in a process scientists call neurogenesis.
There are three types of neuroblastomas, and they're categorized based on the size and shape of the tumor cells: undifferentiated, poorly differentiated, and differentiating neuroblastoma.
Like other embryos, turtle embryos are made of undifferentiated cells that become specific cell types, and then organs and tissues, through gene activity and communication between cells.
An undifferentiated neuroblastoma is mostly comprised of neural crest cells, which are sometimes called small round blue cells, due to a lack of cytoplasm, and a large blue nuclei.