Chest x-ray shows calcifications. Advised TB skin. No symptoms of TB. Matter of concern?

Greetings, My 24 yr old son will be going to Japan in the fall as an exchange student. Just went for physical.MD said chest xray had some areas if calcifications ,and needed a tb skin for a follow up. My son has always been healthy..chronic allergies,over weight,sedentary life style. None of the signs/symproms of tb..is this just a routine physical thing or should I be further concerned...He is finishing up his fourth year at University studying Japanese,has several Japanese in his class and as instructors. I know tb is found in citizens of foreign countries.