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SEER Inquiry System - Report
Produced: 09/15/2025 10:00 AM
Question 20230060
Inquiry Details
References:
#1: WHO Class Urinary System and Male Genital Organs, online. 5th edition
#2: Subject matter expert
Question:
Histology--Urinary: How is histology coded for a diagnosis of bladder carcinoma with a mix of different urothelial carcinoma subtypes? See Discussion.
Discussion:
The 10/2023 TURBT final diagnosis is “Urothelial carcinoma with mixed histologic appearances, see synoptic summary below for details.” The synoptic report includes, “Histologic Type Comment: Invasive carcinoma percentages: Micropapillary 60-70%, high grade or poorly differentiated urothelial 20-30%, squamous 10-20%.” The squamous component is stated to be “Urothelial carcinoma with squamous differentiation.”
It appears there are two specific urothelial carcinoma subtypes to consider: Urothelial carcinoma, micropapillary variant (8131/3) and poorly differentiated carcinoma (8020/3). The squamous component would not be considered because there is no specific histology for “squamous differentiation.”
The micropapillary component is the predominant histology (60-70%) in this case, and it does seem like this is important to capture. However, the WHO Blue Book indicates poorly differentiated carcinoma of the bladder has a poor prognosis.
Answer:
Code histology as urothelial carcinoma, NOS (8120/3). Our subject matter expert advises that WHO Classification of Urinary and Male Genital Tumors, 5th edition, does not recognize mixed urinary histologies; therefore, has not assigned an ICD-O code for urothelial mixed with multiple variants. Only pure variants are coded as they have a different prognosis from those that are mixed. According to WHO, invasive urothelial carcinoma is remarkable for its diversity of morphological appearances and a single lesion can display an admixture of conventional urothelial and various well-defined histological subtypes.
