The Approach External is identified by letter "X" and occupies the 5th position in the ICD10-PCS procedure code structure.
Below a selection of ICD 10 PCS codes related to 0C54X
Destruction of Buccal Mucosa, Open Approach
Destruction of Buccal Mucosa, Percutaneous Approach
Destruction of Buccal Mucosa, External Approach