Coin shadow appered in x-ray?

HRCT stands for "high resolution CT scan". It is a very good diagnostic technique for showing infinitely more detail than the x-ray has shown. You have a very small round shadow resembling a coin (hence the term "coin shadow) on your x-ray. Believe it or not, the fact that the margins are smooth is in your favor, as well as no umbilication. There are many causes for this, including past history of lung infection, pneumonia, etc., that do not involve anything malignant. Interstitial lung disease is also a cause. You don't mention if you are having or have had breathing problems lately. Sometimes scarring from a past respiratory infection could also leave this type of shadow. Have the test and find out for sure before you start worrying needlessly. Good Luck.