Rewritten Instructions

The coding instructions in the front of the book are being rewritten, clarified, and made more user-friendly.


Morphology terms have five-digit code numbers ranging from 8000/0 to 9989/1. The first four digits indicate the specific histologic terms (Table 8).

The fifth digit, after the slash or solidus (/), is a behavior code, which indicates whether a tumor is malignant, benign, in situ or uncertain whether malignant or benign.

A separate one-digit code for histologic grading or differentiation is provided

Structure of a Morphology Code

Structure of a Morphology Code

Example of Revised Wording

Old Wording

If a diagnosis indicates two different degrees of grade or differentiation (e.g., "well and poorly differentiated" or "grades II-III"), code to the higher grade.

New Wording

Grading or differentiation code: Assign the highest grade or differentiation code described in the diagnostic statement.