At this stage, we speak of pluripotent cells, capable of differentiating into any cell, neurons, heart cells, liver cells, etc. Some cells, however, retain this ability to multiply. They are called stem cells and their role is to replace the cells in our body that die during our life.
The vast majority of cells then receive a second signal that directs them to a particular location, such as the brain, liver, heart, etc.
Then a 3rd signal from the organ itself leads to their differentiation into a particular cell type with very specific functions and morphology, for example in the brain, neurons, oligodendrocytes, astrocytes….
By adulthood, the vast majority of our body’s cells are highly specialised and have lost their ability to proliferate.
At the origin of tumours in the brain or in any other organ, we observe a reappearance of the cells’ ability to multiply ad infinitum. These cells multiply anarchically and continuously, forming a cluster known as a tumour.