NAACCR Item #2810: CS Extension

Item # Length Source of Standard Year Implemented Version Implemented Year Retired Version Retired
2810 3 AJCC 2003 10

NAACCR XML: Tumor.csExtension

Identifies contiguous growth (extension) of the primary tumor within the organ of origin or its direct extension into neighboring organs. For certain sites such as ovary, discontinuous metastasis is coded in CS Extension.
Tumor extension at diagnosis is a prognostic indicator used by Collaborative Staging to derive some TNM-T codes and some SEER Summary Stage codes.
Codes (See the most current version of the Collaborative Stage Data Collection System (,13 for rules and site-specific codes and coding structures.)
Note: For cases diagnosed prior to 2010, this was a 2 character field in CS version 1 which was converted to a 3 character field in CS version 2. Most 2 character codes were converted by adding a zero as the third character. For example, code 05 was usually converted to 050, 10 to 100, 11 to 110, etc. Special codes such as 88 and 99 were usually converted to 888 and 999, respectively.