Lung Cancer
noun
肺 is lung, がん is "cancer," I suppose because you want it gone (がん) from you. That makes this word lung cancer, which, with all the smoking in Japan, happens a decent amount.
はいがん
The reading is the same as what you learned with the kanji.
君の辛さはすごく分かるよ。僕も肺がんなんだ。
I really understand what you’re going through because I also have lung cancer.