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SEER Inquiry System - Report
Produced: 12/16/2025 7:34 AM
Question 20210040
Inquiry Details
References:
Solid Tumor Rules. Breast; December 2020 Update
Question:
Solid Tumor Rules (2018, 2021)/Histology--Breast: How is histology coded for a diagnosis ofmixed mucinous carcinoma? See Discussion.
Discussion:
Patient was diagnosed with invasive ductal carcinoma with mucinous features in February 2021, left breast biopsies at 2:00 (3 cm from nipple) and 3:00 (8 cm from nipple) positions. Intraductal component was absent in those specimens.
Subsequent left breast total mastectomy in March 2021, provided a final diagnosis of multifocal mixed mucinous carcinoma, grade 1, 27 and 8 mm and ductal carcinoma in situ (DCIS), low to intermediate grade, with focal mucinous features. The Staging Summary lists Histologic Type as mixed mucinous carcinomafor both foci of invasive carcinoma. DCIS is also noted as present negative for extensive intraductal component.
There does not appear to be a clear instruction or code for this histology. As a central registry, we are unable to follow-up with the pathologist regarding this diagnosis.
Just to be clear, there are 2 foci of invasive mixed mucinous carcinoma in this case measuring 27 mm and 8 mm. The DCIS component measured 56 mm.
Answer:
If the DCIS is separate from the mucinous, apply the breast M rules and abstract TWO primaries per M14. Since all we know of the “mixed mucinous” is there is mucinous present, code 8480/3.
