This is a list of 21 States that honor your Ma. LTC. Be advised that this list can change without notice from year to year so before you travel to any of these states give their State House a call and ask for the firearm licensing division to confirm that they still honor the Ma. license.
You may want to take a look at this also; 12 States Closer To Carry Conceal Gun Laws, No Permit Required
And if you want to see what states honor the Multi state licenses scroll down the information at my States tab.