What can happen if you inject the tumor cells in complete medium?...

ok. Thank you very much for your advice and quick reply.

The fluid will be absorbed. However, it may support the cells initially. My only point is that you haven't strictly tested the cells' ability to grow tumors independent of additional supplements.

In which way may the tumor growth depend on the serum? Will not it be drain out if it is in small volum(100ul)? Thx

You should be consistent between, but I expect the experiment will work. It should also be acknowledged that tumor growth may depend on serum and medium.