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SEER Inquiry System - Report
Produced: 01/13/2026 3:00 PM
Question 20210056
Inquiry Details
References:
#1: Solid Tumor Rules. Breast; December 2020 Upadate
#2: 2021 SEER Manual, 101. Behavior Code
Question:
2018 Solid Tumor Rules/Multiple Primaries--Breast: How many primaries should be reported when a left breast simple mastectomy identifies focal Paget disease of the nipple and 12 axillary nodes positive for metastatic lobular carcinoma (no primary lobular breast tumor identified)?
Discussion:
Answer:
Abstract two primaries, one lobular carcinoma (8520/3) and another one Paget disease of the breast (8540/3) using the 2018 Breast Solid Tumor Rules, Rule M9: Abstract multiple primaries when the diagnosis is Paget disease with underlying tumor which is NOT duct. Example: Paget disease of the nipple with underlying lobular carcinoma are multiple primaries. Additionally, Table 2, Histology Combination Codes, Note 2 states: Lobular carcinoma and Paget are separate primaries (see Lobular carcinoma and any histology in Table 3 with exception of duct carcinoma/carcinoma NST/DCIS (and subtypes/variants) 8500 and Paget disease, in situ and invasive).
While not identified in the pathology of the mastectomy, the lobular carcinoma is likely underlying as it was identified in the axillary lymph nodes. The 2021 SEER Manual states: If the only pathologic specimen is from a metastatic site, code the appropriate histology code and the malignant behavior code (/3). The primary site and its metastatic site(s) have the same histology.
