California Cancer Reporting System Standards Volume I: Abstracting and Coding Procedures for Hospitals
Each patient in a hospital's cancer registry is identified by a permanent nine-digit accession number and each of the patient's primary tumors is identified by a different two-digit sequence number. The accession number remains the same in every abstract prepared by the hospital for the patient, but the sequence number is different.
The first four digits of the accession number usually represents the year first seen for the patient. See Section II.3.1.
The last five digits usually represent the approximate chronological order of the abstracts prepared for that year.
Each facility abstract must contain an accession number and each patient can only have one accession number.
Check to see if the patient already has an accession number, then use that number when it is available.
Assign an accession number only when the patient did not have one assigned previously.