What's the Same
No Topography Changes
The first edition of ICD-O was published in 1976, and a substantial revision - primarily of the topography codes - was published in 1990. There are no changes to any of the topography terms or codes in ICD-O-3.
The Matrix Principle
Although many more specific diagnoses and code-behavior combinations have been added to ICD-O-3 to accommodate electronic reference files, the matrix principle that was introduced in the first edition of ICD-O should be reinforced as another coding tool. The matrix concept is the rule that says it is permitted to change the behavior code of a reported diagnosis so that it truly reflects what the pathologist describes as the behavior. Thus if a pathologist reports a diagnosis of "malignant adrenal rest tumor," the coder may take the 4-digit histology code for adrenal rest tumor, 8671, and change the behavior code /0 to /3. While this will probably generate an edit check or advisory message in a computerized registry database, the system should have the ability to over-ride the message and save the case with a histology-behavior combination that is not printed in ICD-O-3.
Old Terms, New Meanings
Because of changes in the terminology used by pathologists, there is some potential for confusion by non-physicians and coders. For example, pathologists use the term "grade" as a synonym for "type" or "category." Registrars, on the other hand, recognize the term "grade" as an indicator of cell differentiation which is coded in the 6th digit of the ICD-O morphology code. Therefore, it is important to recognize when the term "grade" refers to category and when it refers to biologic activity.
Similarly, to a pathologist, the terms "adult" and "mature" describe cell characteristics rather than the age of the patient. "Transitional" has two meanings: it could be a cell type, or it could be a neoplasm that is converting to something else. Careful communication and explanation of new terms is necessary to assure that the new information is coded correctly.