Well, is have or had
If you have just been diagnosed, a lot depends on whetehr it is resected and what they found, or not resectable and confined to chest, or spread elsewhere.
If it is a diagnosis from some time ago, it depends on how long. If you are about to be married in the upcoming years, you shuold put the cards on the table with your prosepctive spouse. Keeping the fiance in the dark is not very trusting.