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SEER Inquiry System - Report
Produced: 09/17/2025 10:29 PM
Question 20230017
Inquiry Details
References:
#1: Solid Tumor Rules. Colon, Rectosigmoid, and Rectum, September 2021 update
#2: WHO Class Digest System Tumors, 209-211. 5th edition
Question:
Solid Tumor Rules/Multiple Primaries--Rectum/Anal Canal: How many primaries are accessioned and how should histology be coded for a 2021 abdominoperineal resection showing invasive adenocarcinoma of distal rectum and associated Paget disease of the anal mucosa and perianal skin? See Discussion.
Discussion:
The synoptic report calls this “Invasive adenocarcinoma with secondary Paget disease of anal mucosa and perianal skin.” The tumor size is listed as “2.1 x 1.7 x 0.7 cm, including associated advanced adenoma; size does not include the extent of the associated Paget disease, which extends for at least 2 cm distally.” Clinically this is called an incidentally discovered Paget’s disease.
It is unclear if this is a collision tumor that should be abstracted as separate primaries, or if this is a single tumor with underlying Paget’s disease (similar to that described in Other Sites Rule H26). If this is a single rectal tumor, there does not appear to be an H rule for this scenario.
Answer:
Abstract two primaries using rule M4 of the Colon rules or rule M13 of Other Sites: 1. Invasive adenocarcinoma of distal rectum and 2. Paget disease of the anal mucosa / perianal skin (determine site of origin and code primary site accordingly). The rectum and the anus are separate sites and the histologies differ in each site.
The WHO Classification of Digestive System Tumors, 5th edition, states that in addition to secondary anal Paget disease arising from anal canal adenocarcinoma, or rarely, adenoma without documented invasive disease, secondary Paget cells may be contiguous with the underlying neoplasm or manifest at different at sites distinctly away from it (with skip lesions). Document the details in the appropriate text fields.
