Tropical Area, especially South East Asia... Scars in the lungs are occured during Childhood suffering from Chicken Fox or Measles, when it cured it leaves a Scar.. When you become an Adult, it won't be removed unless you go for a Surgery.
In your case you can still travel to Qatar but you have to get authority from your Doctor that this Scar is not a communicable disease and under medication.
For your Employer, if he realy realy needs you he will give you a letter authority to travel and you have to submit to Qatar Embassy along with the Doctors Cert.