FIGURE 4.

Theoretical comparison among avascular tumors (A), tumor spheres (B), and normal blastocysts (C) A. Avascular tumors (as in vivo abnormal blastocysts): external proliferating cell layers (light-blue color), middle quiescent cells (gray color) and necrotic core cells (dark colors) are depicted. B. Tumor spheres (as in vitro abnormal blastocysts): a layered cell distribution, like in avascular tumors, a peripheral cell layer, similar to the blastocyst trophectoderm, and an inner cell cluster, similar to the blastocyst ICM can be observed; shedding bodies from the sphere surfaces can also be noted (modified and adapted from Bond et al., Plos One. 2013). C. Normal hatching blastocysts (as in vitro embryos): trophectoderm, ICM (embryoblast) and blastocoel cavity are indicated, together to the “zona pellucida” (modified from: Human blastocyst hatching. Credit: K. Hardy. CC BY).