I'm needing some help in billing frozen sections. I'm gonna be as short and clear as possible!

Our group employs several pathologists within the Missouri and Illnois areas. One of our Illinois pathologists travels to a dermatology clinic and performs frozen sections. If a patient has Medicare, do we bill the frozen section to Illinois Medicare? And what place of service? 11? With the derm clinic info in Box 32?

The specimens are then sent to our Missouri office where we process the tissue and then a different pathologist reads the slides. Do those charges get billed to Missouri Medicare? With an 81 POS?

Another scenario we have is that a pathologist does a frozen section in a hospital (sometimes the patient is an outpatient and sometimes they are inpatient), but it was performed at the hospital. What POS should be used on these claims?

Any and all help is appreciated. Thank you!