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SEER Inquiry System - Report
Produced: 11/04/2025 11:11 AM
Question 20041022
Inquiry Details
References:
ICD-O-3, 79
Question:
Primary site/Histology (Pre-2007)/Behavior: What is the correct site and histology/behavior for the following diagnosis: "mucinous cystadenoma of the appendix with perforation and pseudomyxoma peritonei." This was diagnosed at e-lap for a separate adenocarcinoma of the ascending colon.
Discussion:
Answer:
For tumors diagnosed prior to 2007:
The appropriate code for mucinous cystadenoma of the appendix with perforation and pseudomyxoma peritonei is C18.1 8470/0. It is not reportable to SEER. According to our pathologist consultant, mucinous cystadenoma is a legitimate term for such appendiceal tumors. They may implant all over the peritoneum as pseudomyxoma peritonei, especially in the face of perforation, without being histologically malignant.
For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.
Cancer Site Category:
N/A
Data Item Category:
Primary site, Histology, Behavior
Other Category:
N/A
Year:
2004
