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SEER Inquiry System - Report
Produced: 09/08/2025 12:06 PM
Question 20180089
Inquiry Details
References:
#1: WHO Class Digest System Tumors, 123
#2: Subject matter expert
Question:
Reportability--Appendix: Is disseminated peritoneal adenomucinosis (DPAM) reportable when it is being referred to as if the primary tumor is a low-grade appendiceal mucinous neoplasm (LAMN)? See Discussion.
Discussion:
Example 1: 8/23/2017 debulking path diagnosis of low-grade appendiceal mucinous neoplasm (LAMN) with involvement of intrapelvic mucin, left ovarian mass, uterine serosa and pelvic tumor, consistent with disseminated peritoneal adenomucinosis, that may also be called low-grade mucinous carcinoma peritonei. 8/8/2018 resection of sigmoid and rectum, path diagnosis of peri-colorectal fibroadipose issue with low-grade mucinous carcinoma compatible with the prior diagnosis of pseumomyxoma peritonei with low-grade mucinous carcinoma histology.
Example 2: Path diagnosis of low-grade appendiceal mucinous neoplasm in association with low grade mucinous carcinoma peritonei involving the serosa of the small intestine and mesentery. Also, there is involvement of serosal lined soft tissue of peritoneum, omentum, stomach, falciform ligament, gallbladder, diaphragm and spleen.
Some pathologists in our area are referring to DPAM as mucinous carcinoma peritonei, which is causing confusion because the term carcinoma is being used. One would assume that because the pseudomyxoma peritonei/underlying tumor itself is low-grade (LAMN), then the case is not reportable, but we would like clarification.
Answer:
For cases diagnosed prior to 1/1/2022
Disseminated peritoneal adenomucinosis (DPAM) is not reportable when the primary tumor is a low-grade appendiceal mucinous neoplasm (LAMN).
The term disseminated peritoneal adenomucinosis (DPAM) is discouraged by the WHO Digestive System monograph (page 123, section on pseudomyxoma peritonei (mucinous carcinoma peritonei)), since it does not clarify whether the process is low grade or high grade carcinoma. When used, the term should be referring back to the histology of the defining process and in both of these examples this appears to be LAMN, and therefore not reportable. The only exception to this might be if the peritoneal implants were invasive; that is, they contained adenocarcinoma invading into the underlying peritoneum, bowel serosa, etc., rather than simply being present within the surface mucinous material. The pathologist would make this clear if this was, in fact, believed to be invasive carcinoma.
