Case report: Bladder carcinoma with shadow cell differentiation: a case report with immunohistochemical analyses

Bladder carcinoma encompasses various histological subtypes, with shadow cell differentiation (SCD) being an exceptionally rare occurrence, resembling cutaneous pilomatricoma. Herein, we report a case of bladder carcinoma with SCD and aim to elucidate its clinico-pathological characteristics. A 67-year-old North African man, a heavy smoker, who presented with left lumbar pain, haematuria and dysuria. The physical examination revealed a hypogastric mass. Rectal examination was unremarkable. Radiological examination (Ultrasound and CT) showed a 3 cm bladder tumor, with a suspicious lung and mediastinal tumors. A complete transurethral resection of the bladder tumor (TURB) was performed. It showed high-grade urothelial carcinoma with partial squamous differentiation and SCD. Immunohistochemistry revealed positive β-catenin in the peripheral squamous component. Our findings highlight that SCD, a form of keratinization typically observed in the hair matrix, can also manifest in carcinomas with squamous components. The presence of SCD in these tumors suggests a variant of keratinization potentially linked to the squamous components within these neoplasms. We presented a case bladder carcinoma with SCD, underscoring its unique histopathological features and the importance of recognizing this rare variant for accurate diagnosis and management.