Am I allowed to go out of airport to meet a friend in Istanbul while I travel from UK to Cairo?

Does anyone know how the procedure goes in airports...I am planning to fly from Manchester, UK to Cairo, Egypt and would like to know that am I allowed to meet my friend in Istanbul where I will have land over of 12 h in Istanbul before continuing my flight to Cairo? I have finnish passport and would like to ask do I need to have visa also to Turkey if I just stay for less than 10 h there? I would be pleased if anyone would know about this. Thank you!