A large number of asymmetric divisions are involved in making a multi-cellular organism out of a single zygote. At each point of branching of these myriad cell lines is a progenitor cell which is termed the stem cell. The rest branch out from it. Also, the potential for growth in the cells at these early stages of development is almost infinite, comparable only to cancerous cells. Many morphogens which regulate development share common structural features with proto-oncogenes and oncogenes. Completing
the beautiful threesome of multi-cellular life
, cancer cells have certain cancer stem cells, which lead to revival of tumours after every therapy.
Here is a video highlighting the relation between cancer and stem cells