We subscribe to the Pathology Coding Service Handbook published by the American Pathology Foundation, which updates quarterly. I think it is reasonably helpful.
The University of Michigan has a good CPT code quick list: https://www.pathology.med.umich.edu/intra/pdfs/SpecimenCPTCribSheetMarch2011.pdf
This of course doesn't touch on more complex questions like "when is a lymph node a regional resection?"
Much more complete, and very well-written, is the APF's Pathology Service Coding Handbook. This has the disadvantage, however, of not being free on the internet.
Finally, if you're not in a hurry, there is this here forum, which I have found to be a useful resource to find out how everyone else is handling specific specimens.