| Item # | Length | Source of Standard | Year Implemented | Version Implemented | Year Retired | Version Retired |
|---|---|---|---|---|---|---|
| 1,971 | 4 | SEER |
Area for retaining the histology portion (4 digits) of the ICD-O-1 or field trial morphology codes entered before a conversion to ICD-O-2. The item name includes years 1973-91. However, some states may have used the codes for cases before 1973.