Primary Urethral Clear-Cell Adenocarcinoma Comprehensive Analysis by Surgical Pathology, Cytopathology, and Next-Generation Sequencing

Primary clear-cell adenocarcinoma of the urethra, a rare tumor that histomorphologically resembles clear-cell carcinoma of the female genital tract, occurs predominantly in women and is associated with a relatively poor prognosis. The histogenesis of this rare urethral neoplasm has not been completely resolved, but it is thought to arise from either müllerian rests or metaplastic urothelium. Herein, we present comprehensive surgical pathological and cytopathological findings from a patient with primary urethral clear-cell adenocarcinoma and describe next-generation sequencing results for this patient's unique tumor—the first such reported characterization of molecular aberrations in urethral clear-cell adenocarcinoma at the transcriptomic and genomic levels. Transcriptome analysis revealed novel gene fusion candidates, including ANKRD28-FNDC3B. Whole-exome analysis demonstrated focal copy number loss at the SMAD4 and ARID2 loci and 38 somatic mutations, including a truncating mutation in ATM and a novel nonsynonymous mutation in ALK