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SEER Inquiry System - Report
Produced: 01/31/2026 11:17 AM
Question 20240037
Inquiry Details
References:
#1: WHO Class Urinary System and Male Genital Organs, 394-396. 5th edition
#2: Solid Tumor Rules. Urinary Sites, 2024 Update
Question:
Solid Tumor Rules/Histology--Bladder: How is histology coded for a bladder tumor when the diagnosis is 95% large cell neuroendocrine carcinoma and 5% high grade urothelial carcinoma of no special type? See Discussion.
Discussion:
In the 2024 Solid Tumor Rules update, the small cell neuroendocrine carcinoma row in Table 2 was changed. The NOS histology became neuroendocrine carcinoma, NOS (8246) and both large cell and small cell neuroendocrine carcinomas (8013 and 8041, respectively) became the subtype/variants. This change impacts Rule H4 but Rule H4 was not updated. Rule H4 still refers to small cell neuroendocrine carcinoma as being the NOS histology.
In the prior STR versions, it was clear the tumor in question would be coded as 8045 per Rule H4 and Table 2. Considering Rule H4 was not updated according to the changes for Table 2, does histology 8045 still apply to this diagnosis?
There is currently no way to arrive at a histology for this case. Does Rule H4, bullet 3 need to be updated to indicate, “subtype/variant of neuroendocrine carcinoma mixed with any other carcinoma (does not apply to sarcoma)”?
Answer:
Assign 8013/3 (combined large cell neuroendocrine carcinoma). There are two histologies present: large cell NEC and urothelial. Literature search found primary large cell NEC of the bladder is extremely rare with less than 20 reported cases. This case does not fall into the site-specific rules and given it's raity, a specific rule for this situation was not and will not be added to the Bladder rules. See #1, Example 2, in the general instructions for coding histology.
