SEER Extent of Disease Coding

SEER Extent of Disease (EOD) coding has gone through several revisions and now includes schemes for all sites of cancer. The EOD coding scheme consists of a ten-digit code. It incorporates three digits for the size and/or involvement of the primary tumor, two for the extension of the tumor, and one more as a general code for lymph node involvement. Four more digits are used after these six: two for the number of pathologically positive regional lymph nodes and two more for the number of regional lymph nodes that are pathologically examined. The code is based on clinical, operative, and pathological diagnoses of the cancer. The size of tumor recorded is the size before systemic (i.e., chemotherapy) or radiation therapy. Examples for tumor extension codes for the colon are shown in the table below.

As depth of invasion increases in a site the extension code increases. It is important to review the extent of disease (EOD) codes and coding instructions at the time of abstracting in order to ensure accuracy. Each site has a different scheme.

Regional lymph nodes are listed for each applicable site. Regional lymph nodes do not apply to sites such as the brain, lymphoma, and the hematopoietic system. These cancers induce leukemia, multiple myeloma, and other hemoatopoietic and reticuloendothelial neoplasms. The lymphoma scheme reflects systemic symptoms at diagnosis. Positive and examined regional nodes are not applicable to these sites.

The EOD coding scheme provides a value, or code, for the lymph node field for all sites. Adjacent (regional) lymph nodes may be classified by size, laterality, number of nodes involved, and the distance of the nodes from the organ of origin. Lymph node involvement is also a hierarchical code.

When lymph nodes are described as fixed, matted, or mass, they are considered to be involved with tumor. Terms such as palpable, enlarged, or lymphadenopathy do not indicate involvement in solid tumors. A clinical or pathological statement must verify the presence of tumor. When staging lymphomas, however, any of these terms indicate involvement. Nodes that are part of a resected primary site specimen should be considered regional nodes.

The extent of disease coding scheme records the number of regional nodes found positive for cancer at pathological examination. The number of regional lymph nodes pathologically examined must also be recorded.

The EOD coding system also includes schemes for Kaposi's sarcoma and mycosis fungoides and Sezary disease. There is no staging system for this disease in the American Joint Committee on Cancer staging system.