The proposed resolution follows lengthy discussion with the submitter and SMEs in the mCODE Technical Review Group: It was agreed that the original description of the issue was not entirely clear. The issue is really whether it makes sense to allow for separate morphology and behavior codes, and if so, is it better to have two extensions or change the existing extension to 0..*. For ICD-O-3 encoded diagnoses, we currently recommend putting the morphology code and the behavior code together, following common convention, e.g. 8410/2. This could be separated into morphology (8410) and behavior (2). However, this is not common practice and not the way most systems represent ICD-O-3. Therefore, a change is not required or recommended. For SNOMED CT encoding, the STU 2 representation requires a code that precoordinates morphology and behavior. In most cases, the required codes are available, and Scott Campbell is developing and submitting codes that are currently missing. Furthermore, in many cases the post-coordinated codes that would result from forcing the separation of morphology and behavior are NOT available (e.g., there is no code from adenocarcinoma, only codes for adenocarcinoma in situ and malignant adenocarcinoma. Separating the current field into 2 fields might cause more problems than it solves. Changing from 0..1 to 0..* is not backward compatible, and that is a concern for implementers. For registry reporting where ICD-O-3 is required, mappings between SNOMED and ICD-O-3 are available. Based on these considerations, it was decided to not make a change to the cardinality or add another extension for behavior.  An error was noted in the documentation on this page where the Condition.code for ICD-O-3 is described. This will be fixed.