Equivalent or Equal Terms

In the General Instructions, there are two sets of terms listed under "Equivalent or Equal Terms". They are:

• Multicentric, multifocal
• Tumor, mass, lesion, neoplasm

What the first item means is that "multicentric" and "multifocal" mean the same thing for the purposes of the multiple primaries and histology coding rules. These terms are interchangeable for all rule sets, unless otherwise noted. These word groups could also be stated as

• Multicentric = multifocal
• Tumor = mass = lesion = neoplasm

These definitions are based on extensive discussions with the physicians on the MPH task force. Although there may be differences in the technical or biological definitions of the terms, the clinicians decided that it was not worth the registrar's time and effort to infer any distinction between them, since the differences do not affect the rules.

Note that, in the multiple primaries and histology coding rules, a statement may refer to a tumor or mass or lesion or neoplasm, and the terms can be used interchangeably. However, none of those terms would be considered a reportable case under the current case ascertainment rules (unless the case was a benign or borderline central nervous system tumor). Thus it is very important to remember and understand that the word lists in these rules are intended for the purposes of determining multiple primaries and coding histology only.

Each site-specific section will also include a set of site-specific equivalent or equal terms for that site only. For example, in the breast rules, equivalent or equal terms section,

• Duct = ductal
• Mammary = breast

and in the head and neck rules,

• In situ = noninvasive = intraepithelial
• Squamous cell carcinoma = squamous cell epithelioma = epidermoid carcinoma
• Contiguous = continuous

The words in these groups can be used interchangeably.