Are there any differences between a Diff. Amp and a current sense Amp?

If So, what are they? I notice that right along side a current sense amp is a diff. amp in catalogs, So whats the difference? If Im just monitoring how much current Im using using a sense resistor, wouldnt a diff amp do just as good?

Ive been having trouble finding a current sense amp that has a Gain of 100 and is available in through hole form that Mouser sells. The reason for using mouser other than digikey is because I need a PIC18F1320 for a project, and I refuse to pay $5 for it at digikey when I can get it for Much Less at mouser.

They are similar but not identical.

A current sense amp is usually designed to monitor voltage across the current sense resistor at the rail while being powered by the rail. A diff amp will need to have a common-mode voltage range equal to the rail voltage to sense the rail current. Many do not.

To sense small voltages across the current resistor on the rail requires a high value of common-mode rejection to avoid offset errors in the measurement. Diff amps may not have sufficient rejection to keep this error at a reasonable value.