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SEER Inquiry System - Report
Produced: 02/13/2026 3:09 PM
Question 20230041
Inquiry Details
References:
Solid Tumor Rules. Breast, 2023 Update; May 2023 Update
Question:
Solid Tumor Rules/Multiple Primaries--Breast: Is an in situ tumor followed by an invasive tumor a single or multiple primaries? See Discussion.
Discussion:
In the examples below, are these a single or multiple primaries?
Example 1:
Tumor 1: C509/left breast, 8520/2 (in situ lobular carcinoma), dx date-01/10/2019
Tumor 2: C509/ left breast, 8500/3 (carcinoma NST), dx date-08/19/2021
Example 2:
Tumor 1: C509, right breast, 8520/2, dx date 06/26/2014
Tumor 2: C508, right breast, 8500/3, dx date-05/23/2019
There seems to be some conflicting info on this. In the 2020 Breast Rules there was a note add to the revision history. “M10 Same behavior requirement re-added.” Which is not in the rules now, nor was it noted to the revision changes in the last two change logs.
Inquiry 20200070 would seem to indicate that this is multiple primaries, but that contrasts with 20230010 which would seem to indicate a single primary, and an ASK A SEER Registrar question that we received a response to. I don’t see a scenario where rule M17, an invasive tumor DX more than 60 days after an in situ tumor would come into play.
If behavior no longer applies to rule M10, at what point did that change get made? Please advise.
Answer:
Abstract a single primary when there are multiple tumors of carcinoma NST/duct and lobular using the current Breast Solid Tumor Rules, Rule M10, May 2023 Update, for cases diagnosed 01/01/2018 and forward in the examples provided. The rule also notes to follow the H rules to determine the correct histology code when a mixture of behaviors is present in carcinoma, NST and lobular carcinoma. Rule M5 does not apply as the timeframe is less than 5 years in both examples.
The 2023 update for the Breast Solid Tumor Rules (released November 2022) states: The rules for determining single versus multiple primaries in tumors with carcinoma NST/duct and lobular carcinoma have been revised and now align with ICD-O-3.2. Applicable Histology Rules have also been revised to reflect ICD-O-3.2 histology terminology and corresponding ICD-O codes.
