Differences between ICD-O & ICD-10

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 Figure 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.

Figure 2. ICD-10 Alphabetic Index Entry for Lung Neoplasms
  Malignant Secondary or Metastatic In situ Benign Uncertain and Unknown
Lung C34.9 C78.0 D02.2 D14.3 D38.1

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. Figure 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 Figure 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.

Figure 3. ICD-O Coding of Lung Neoplasms
Lung Neoplasm Topography Code Behavior Code
Malignant neoplasm of the lung (such as carcinoma) C34.9 M-8010/3
Metastatic neoplasm of the lung (such as metastatic seminoma from the testis) C34.9 M-9061/6
In situ neoplasm of the lung (such as squamous carcinoma in situ) C34.9 M-8070/2
Benign neoplasm of lung (such as adenoma) C34.9 M-8140/0
Uncertain behavior of neoplasm of lung (such as carcinoid of uncertain behavior) C34.9 M-8240/1

*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.

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

Figure 4. ICD-O Behavior Code and Corresponding Section of Chapter II, ICD-10
Category Term
/0 D10-D36 Benign neoplasms
/1 D37-D48 Neoplasms of uncertain and unknown behavior
/2 D00-D09 In situ neoplasms
/3 C00-C76,
Malignant neoplasms stated or presumed to be primary
/6 C77-C79 Malignant neoplasms, stated or presumed to be secondary