Review: ICD-O Structure & Format
Here is what we have learned from ICD-O Structure & Format:
- ICD-O is a dual classification with coding systems for both topography and morphology.
- In ICD-O, the topography code describes the site of origin of the neoplasm, and the morphology code describes the cell type of the tumor and its biologic activity.
- ICD-O consists of five main sections:
- Instructions for Use
- Topography-Numerical List
- Morphology-Numerical List
- Alphabetic Index
- Differences in Morphology Codes between ICD-O-3 and ICD-O-2
- The topography section has been adapted from the malignant neoplasm section of Chapter II of ICD-10.
- ICD-O topography terms have four-character codes that run from C00.0 to C80.9. A decimal point (.) separates subdivisions of the three-character categories.
- Each topographic and morphologic term appears only once in the numerical list, and the first listed term, printed in bold type under a particular code, is the preferred term.
- Morphology terms have five-digit codes ranging from M-8000/0 to M-9989/3 with the first four digits indicating the specific histologic term and the fifth digit used as a behavior code.
- Following the behavior code, a separate one-digit code is provided for histological grading or differentiation.
- The alphabetic index is used to code topography and morphology, which also includes selected tumor-like lesions and conditions.
- The terms are listed under both the noun and the adjective in the alphabetic index.
- In the alphabetic index, any word that appears as part of three or more terms is in bold type.
- Lymphomas and leukemias are exceptions to the rule of listing conditions under all parts of the terms; There is only one list for "lymphoma, malignant" and one for "leukemia."
- ICD-O-3 incorporates terms from the WHO systems as preferred terms for hematologic malignancies, but terms from older systems are retained to permit universal coding and analysis of historical data.
- In order to ensure compatibility with ICD-10, there are a number of ways in which the Third Edition of ICD-O difers from the structure of the WHO classification of hematological malignancies.
- The code for a term followed by "NOS" should be used when:
- a topographic or morphologic term is not modified;
- a topographic or morphologic term has an adjective that does not appear elsewhere; and
- a term is used in a general sense.
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