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Format of ICD-O Terms in Numerical List

Each topographic and morphologic term appears only once in the numerical list, as the examples in Figure 10 demonstrate. The first listed term, printed in bold type under a particular code, is the preferred term.

In this example, "parotid gland" would describe all cases coded to C07.9. The bold type indicates that this is the preferred (first) term. The synonym, "parotid, NOS," is indented under "Parotid gland." The non-indented terms, "Stensen duct" and "parotid gland duct," are called equivalent terms. They are not synonyms of the preferred term (parotid gland) but are listed under the same code number because they are topographic subdivisions of the term listed first and are not sufficiently different to have their own codes. In the alphabetic index all these terms are given the code C07.9. Similarly, for morphology, "oxyphilic adenocarcinoma" would describe all morphologies coded to M-8290/3. "Oncocytic carcinoma" and "oncocytic adenocarcinoma" are other names (synonyms) for "oxyphilic adenocarcinoma," but "Hurthle cell carcinoma," "Hurthle cell adenocarcinoma," and "follicular carcinoma, oxyphilic cell" (equivalent terms) are other types of carcinomas involving the oxyphilic cell.

Figure 10. Examples of Numerical List Format
C07.9 Parotid gland
Parotid, NOS
Stensen duct
Parotid gland duct
M-8290/3 Oxyphilic adenocarcinoma
Oncocytic carcinoma
Oncocytic adenocarninoma
Hurthle cell carcinoma (C73.9)
Hurthle cell adenocarcinoma (C73.9)
Follicular carcinoma, oxyphilic cell (C73.9)