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Produced: 04/22/2026 9:12 PM
Question 20190037
Inquiry Details
References:
Solid Tumor Rules, 27. April 2019 Update
Question:
Solid Tumor Rules/Multiple Primaries--Breast: How many primaries should be abstracted for simultaneously diagnosed non-contiguous invasive duct carcinoma and mucinous carcinoma? Does rule M12 apply since the two histologies are on different rows of Table 3 of the Breast Solid Tumor Rules? See Discussion.
Discussion:
Core biopsy of left breast at 2:00: Invasive ductal carcinoma, Nottingham score 6/9.
Core biopsy of left breast at 4:00: Invasive mucinous carcinoma (variant of ductal carcinoma), Nottingham score 5/9.
Post neo-adjuvant mastectomy: Main (largest tumor): Invasive ductal carcinoma, upper outer quadrant grade 2. Secondary tumor: mucinous carcinoma, grade 1 at 4:00.
Answer:
Abstract multiple primaries when separate, non-contiguous tumors are on different rows in Table 3 of the Breast Solid Tumor Rules. Use Rule M14 as each row in the table reflects a distinctly different histology, in this case, invasive ductal carcinoma (8500) and mucinous carcinoma (8480).
