Basic Differences

Basic Differences

There are basic differences between the structure of ICD-O and that of ICD. In Chapter II (Neoplasm) of ICD, the topography code describes the behavior of the neoplasm (malignant, benign, in situ, or uncertain whether malignant or benign) by assigning it to a specific range of codes identifying each of these types of behavior. As a result, in ICD-10, five different categories of four characters each are needed to describe all lung neoplasms (see Table 2). Very few histological types are identified in ICD. For example, there is no way in ICD to distinguish between an adenocarcinoma of the lung and a squamous cell carcinoma of the lung: both would be coded to C34.9.

The ICD-10 alphabetic index (Vol.3) contains, under the term "neoplasm," a table of five columns with the following headings: Malignant, Secondary or Metastatic, In situ, Benign, Uncertain and Unknown Behavior. Appropriate ICD-10 categories for each site of the body are then listed in alphabetic order. Table 2 shows the entry for lung neoplasms.

In contrast, ICD-O uses only one set of four characters for topography (based on the malignant neoplasm section of ICD-10); the topography code (C34.9, lung) remains the same for all neoplasms of that site. The behavior code, incorporated as the fifth digit in the morphology field, identifies whether the neoplasm is malignant, benign, and so forth. (See Behavior Code) ICD-O also describes the type or morphology of the neoplasm, as shown in Table 3; an adenocarcinoma of the lung would thus be coded C34.9, M-8140/3, and a squamous cell carcinoma of the lung C34.9, M8070/3.

* Note: Cancer registries throughout the world do not use the /6 behavior code (metastatic). Registries report the behavior of the primary tumor, not the metastic tumor. The /6 is used infrequently by pathologists in very few places in the world.

Table 4 shows the correspondence between the behavior code of ICD-O and the different sections of Chapter II of ICD-10.