There is no one right answer for this question.  We normally use pepsin digestion for demonstrating kappa and lambda in formalin-fixed, paraffin-embedded tissue.  However, we have tried HIER using a 96 degree waterbath with success on certain cases.  I have also seen excellent results using a pressure cooker, but in our experience this casues too much section damage.  One of the problems we face is that about half of our Hemepath cases come from other institutions.  Some of these cases show better immunoreactivity than what we can produce on our own material.  Just when you want to give up, you see a case that shows beautiful monoclonal staining which causes momentary excitement and gives you the justification to continue doing these difficult stains.

RWC