They Have Found A Spot At The Top Of My

They have found a spot at the top of my left lung that is 1.5 cm. I will be having a PET SCAN on Tuesday I know that less than a year ago when I had a chest x-ray done for another reason no one saw a spot. My question is if this turns out to be cancer do you think that it was caught early. I have smoked in the past but quit on August 7, 2010 when I had a heart attack and I have 4 stints. I have had a nagging cough for at least the past 40 years and I am 62. My cough happens when I laugh or get over heated. With that information, do you think that this is a serious thing or maybe just some scar tissue from the past