POU2F3-positive small cell neuroendocrine carcinoma of the urinary tract: a clinicopathological analysis of five cases

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The study analyzed five cases of POU2F3-positive small cell neuroendocrine carcinoma in the urinary tract diagnosed between 2023 and 2025.
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All tumors exhibited small round blue cells with high nuclear-to-cytoplasmic ratios and showed loss of conventional neuroendocrine markers.
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Immunohistochemistry revealed diffuse POU2F3 expression in all cases, contrasting with conventional bladder SmCC cases that were negative for POU2F3.
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Next-generation sequencing identified a TP53 missense mutation in one case, indicating potential molecular heterogeneity.
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POU2F3 may improve diagnostic accuracy for urinary tract SmCC with low neuroendocrine marker expression, highlighting a neuroendocrine-low phenotype.

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