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SEER Inquiry System - Report
Produced: 10/20/2025 8:56 AM
Question 20230010
Inquiry Details
References:
Solid Tumor Rules. Breast, 2023 Update
Question:
Solid Tumor Rules/Multiple Primaries--Breast: How many primaries are accessioned when a 2020 diagnosis of invasive ductal carcinoma treated by lumpectomy is followed by a 2023 diagnosis of invasive lobular carcinoma treated by mastectomy? See Discussion.
Discussion:
Historically, multiple invasive ductal and lobular carcinomas diagnosed within 5 years were abstracted as a single primary. However, it is not clear if Rule M10 or M14 applies to this situation per the 2023 Solid Tumor Rules updates.
Rule M10 addresses multiple tumors of carcinoma of no special type (NST)/duct and lobular, but there is no timing criteria mentioned. Does M10 apply to cases diagnosed synchronously, or metachronously, or at least within 5 years? Should Rule M10 include a Note instructing registrars to accession a single primary for the scenario in question?
If timing matters for Rule M10, then the next rule that applies is M14. Rule M14 instructs one to abstract multiple primaries when separate/non-contiguous tumors are on different rows in Table 3, and carcinoma NST/duct and lobular carcinoma are on separate rows in Table 3.
Answer:
Abstract a single primary using the Breast Solid Tumor Rules, Rule M10, assuming the tumors are in the same breast. This rule is specific to multiple tumors of carcinoma NST/duct and lobular. Timing is not a factor in this rule. As stated in ‘New for 2023,’ 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.
Tumors occurring more than five years apart are multiple primaries and would have been caught at Rule M5. Thus, rule M10 pertains to tumors occuring less than five years apart.
