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SEER Inquiry System - Report
Produced: 05/17/2026 6:12 PM
Question 20180083
Inquiry Details
References:
Solid Tumor Rules. Urinary sites, April 2019 Update
Question:
Solid Tumor Rules (2018)/Multiple primaries--Bladder: How many primaries are abstracted and which M Rule applies when a patient is diagnosed with an invasive urothelial carcinoma tumor of the bladder, followed less than three years later by an invasive urothelial carcinoma and small cell neuroendocrine carcinoma tumor of the bladder? See Discussion.
Discussion:
The Solid Tumor Rules indicate bladder tumors that are urothelial carcinoma (8120) and small cell carcinoma (8041) are separate primaries per Rule M13 (Abstract multiple primaries when separate/non-contiguous tumors are on different rows in Table 2). These are distinctly different histologies and, presumably, one would want to capture the small cell carcinoma (or small cell carcinoma component) as this has a worse prognosis.
However, if a subsequent bladder tumor is composed of invasive urothelial carcinoma and small cell neuroendocrine carcinoma, the histology is coded as 8045/3 per Rule H4, but this is not abstracted as a multiple primary. The only M Rule that applies is Rule M18 (Abstract a single primary when tumors do not meet any of the above criteria). The mixed histology code 8045 is not included in Table 2, so none of the histology-based M Rules apply. Is the subsequent mixed invasive urothelial and small cell carcinoma tumor (8045/3) the same primary as a previously diagnosed invasive urothelial carcinoma (8120/3) when these tumors are diagnosed within three years?
Answer:
Abstract two separate primaries using Solid Tumor Rules Urinary Sites Rule M13. While not stated in the urinary sites rules, these are separate histology codes in two different rows in Table 2 of the Rules. The initial histology is 8120 and the subsequent tumor is 8045 using Rule H4.
Adding 8045 to Table 2 will cause issues. Small cell neuroendocrine in the bladder is very rare, extremely aggressive, and usually has a component of urothelial carcinoma.
