Code specifying how the conversion of site and morphology codes from ICD-O-1 and the field trial editions to ICD-O-2 was accomplished. The item names include years 1973-91. However, some states may have used the codes for tumors before 1973. The code also covers morphology conversions from ICD-O-3 to ICD-O-2.

0	Primary site and morphology originally coded in ICD-O-2
1	Primary site and morphology converted without review
2	Primary site converted with review; morphology machine-converted without review
3	Primary site machine-converted without review, morphology converted with review
4	Primary site and morphology converted with review
5	Morphology converted from ICD-O-3 without review
6	Morphology converted from ICD-O-3 with review
Blank	Not converted