SEER Training Modules

Coding T Equivalent

The T equivalent is determined by the tumor size and the tumor extension (direct or contiguous), using the information coded in the fields CS Tumor Size and CS Tumor Extension.

Record the tumor size, using the largest dimension, or diameter of the primary tumor, in millimeters. To convert centimeters to millimeters, multiply the dimension by 10. For example, 2.5 cm = 25 mm, code as 025.

Record the tumor extension, selecting the highest code that describes the farthest extension of the primary tumor.

Refer to both the general guidelines and site-specific instructions for coding the tumor size and tumor extension fields.

View the slide that illustrates how the registrar codes CS to obtain the "T" in "TNM".

Collaborative Stage records more detailed information than TNM or Summary Stage individually because CS is a combination of both staging systems.

Example: T3 in colon cancer


Tumor invades through the muscularis propria into the subserosa or into non-peritonealized pericolic or perirectal tissues.

View the slide that demonstrates the T category equivalent to T3.

Extension into Adjacent Connective Tissues:

Record direct extension to the adjacent tissues, structures, and organs. Some CS schemes contain a code for adjacent connective tissue, which is defined as the unnamed tissues that immediately surround an organ or structure containing a primary cancer. Use this code when a tumor has invaded past the outer border (capsule, serosa or other edge) of the primary organ into the organ's surrounding supportive structures but has not invaded into larger structures or adjacent organs.

Extension into Adjacent Organs:

Organs are anatomic structures with specific physiologic functions other than or in addition to support and storage. Continuous tumor growth from one organ into an organ lying next to the primary organ would be described as extension to adjacent organs/structures, specifically in coding ill-defined and non-specific primary sites.

Extension into Adjacent Structures:

Connective tissues large enough to be given a specific name would be considered adjacent structures. For example, the brachial artery has a name, as does the broad ligament. Continuous tumor growth from one organ into an adjacent named structure would be coded to the appropriate code for "adjacent organs/structures" in the CS staging schemes; for ill-defined or non-specific sites.