According to a recent Transmittal from the Centers for Medicare and Medicaid Services, physicians and others are using modifier -PC to designate the "professional component" of diagnostic tests.  However, the -PC modifier is actually to be used to designate "Wrong Surgical or Other Invasive Procedure Performed on a Patient." 

Apparently many providers assume that because the modifier for technical component services is -TC, the corresponding modifier for professional components is -PC.  In fact, the correct modifier for professional component services is -26.

Note that Claims submitted with the wrong modifier will be denied.