Pathological Features and Immunohistochemical Characteristics of Clear Cell (Glycogen-Rich) Urothelial Carcinoma: A Case Report and Systematic Review of the Literature

Clear cell (glycogen-rich) urothelial carcinoma is an exceedingly rare variant of invasive urothelial carcinoma, distinguished by the presence of abundant cytoplasmic glycogen, which imparts a clear appearance to the tumor cells under histological examination. In this case report, the diagnosis was established through histopathological evaluation with hematoxylin and eosin (HE) staining, immunohistochemical analysis, and the identification of significant cytoplasmic glycogen accumulation. The patient, an 89-year-old male, was admitted on July 24, 2024, presenting with painless gross hematuria persisting for one week. Abdominal ultrasound and CT urography revealed a soft tissue mass on the right side of the bladder wall, measuring 30×30 mm, with a broad base connected to the bladder wall. The mass exhibited significant enhancement on contrast-enhanced scans, raising suspicion for malignancy. Microscopic examination revealed two distinct tumor cell morphologies: the conventional urothelial carcinoma pattern and a clear nest-like morphology, with the latter comprising over 70% of the tumor. Immunohistochemical staining for GATA-3, CK7, PAS, PAS-D, CAIX,PAX8,and RCC confirmed the diagnosis of clear cell (glycogen-rich) urothelial carcinoma. This rare variant of invasive urothelial carcinoma underscores the need for detailed diagnostic analysis to inform prognosis and treatment strategies.