Repeated application of rubbing alcohol followed by blotting with an old towel should work. Apply the alcohol, agitate it a little then blot. A crevice tool of a shop vac will pull the alcohol out faster if you have one available.
If there's any color in the fabric, I would test the alcohol on the bottom of the shirt first to make sure it doesn't cause the dye in the shirt to bleed.
It may take a number of applications to make it disappear.