Important Line in A Fault In Our Stars

In my book, I have notices there has recently been a very important line that develops plot and is a plot twist. This line is, "I lit up like a Christmas tree, Hazel Grace. The lining of my chest, my left hip, my liver, everywhere." (214) This event is when Gus tells Hazel his cancer is back.

This is very important because it completely alters the plot. If Gus didn't get diagnosed with cancer again, then he wouldn't have to worry about his life. Their relationship has completely changed due to this event. 

Also, this has created a new conflict between Gus and his cancer. He will have to fight it in order to stay with Hazel, and most importantly live. Also it has created an emotional conflict for Hazel because she loves him.