High-Grade Urothelial Carcinoma with Divergent Prostatic Differentiation Mimicking a Collision Tumor in a Bladder Diverticulum.
Anna Budina, Norge Vergara, Farah El-Sharkawy Navarro et al.
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Case in brief
A 68-year-old man presented with gross hematuria and a 2.2 cm tumor in a posterior bladder diverticulum. Initial transurethral resection suggested high-grade urothelial carcinoma; repeat resection also showed glands resembling prostatic ductal adenocarcinoma. Diverticulectomy demonstrated urothelial carcinoma with carcinoma in situ and an abutting, focally admixed glandular component expressing prostatic markers. Normal serum PSA and unremarkable prostate MRI argued against a prostatic primary. Targeted sequencing found identical disease-associated variants in both components, supporting a shared neoplastic process with divergent prostatic differentiation.
What made this case unusual
The morphologically and immunohistochemically distinct components mimicked a collision tumor, but shared variants on targeted sequencing supported divergent differentiation within one urothelial neoplasm.
Diagnostic / clinical pearl
When a bladder tumor contains a prostatic-appearing glandular component, morphology and immunophenotype may suggest a collision tumor; targeted molecular comparison can help establish whether the components share a neoplastic origin.
Why it matters
Recognizing divergent differentiation can affect diagnostic classification and has potential prognostic and therapeutic implications.