An official website of the United States government
Home
SEER Inquiry System - Report
Produced: 05/17/2026 4:46 PM
Question 20180061
Inquiry Details
References:
2018 SEER Manual. Appendix C, Coding Guidelines
Question:
Primary Site: How should primary site be coded when there is an invasive tumor in one subsite and an in situ tumor in another subsite of the breast? See Discussion.
Discussion:
The previous SEER Program Coding and Staging Manual included Appendix C that has Coding Guidelines for some sites. The breast guidelines specifically instructed one to code the subsite with the invasive tumor when the pathology report identifies invasive tumor in one subsite and in situ tumor in a different subsite or subsites. The current Breast Solid Tumor Rules Table 1: Primary Site Codes refers one back to the SEER Manual and COC Manual for a source document priority list but does not make mention of invasive vs. in situ on that final version of the source document.
In addition, the Colon Solid Tumor Rules currently contains no Site Coding Section/Table. However, the Lung Solid Tumor Rules do and also refer one to the SEER/COC Manuals for document priority lists. The Urinary Solid Tumor Rules has both the Primary Site Codes Table and an additional section called Priority for Coding Primary Site, which does not reference a document priority list or other manuals. Unfortunately, there is additional information in Appendix C Bladder Coding Guidelines that may have been used in the past regarding site source priority.
Could the remaining applicable Appendix C information be consolidated into the Solid Tumor Rules consistently among all the sites to lessen the need for additional manual referencing? Also, is there a reason one site includes the Priority Site Coding instructions and others do not?
Answer:
Code the subsite with the invasive tumor as the primary site when the pathology report identifies invasive tumor in one subsite and in situ tumor in a different subsite or subsites as stated in Appendix C, Breast Coding Guidelines, 2018 SEER Program Coding and Staging Manual. This statement is unchanged from the previous version; however, the priority list was modified for coding a subsite when there is conflicting information.
The focus of the Solid Tumor Rules is to differentiate between single vs. multiple primaries and to assist with identifying the appropriate histology code. The site tables in the solid tumor rules are a reference only. The site-specific Coding Guidelines assist with additional considerations when abstracting cases.
