Primary Wilms tumor of the urinary bladder

Abstract

Wilms tumor (WT) can occur at various extrarenal sites; however, the urinary bladder as the primary site is occasional. A 4-year-old-female child presented with difficulty in micturition for the past month. The contrast-enhanced magnetic resonance imaging with magnetic resonance (MR) urography revealed a polypoidal, heterogeneous mass in the urinary bladder with no abnormality in the kidneys. Cystoscopy-guided biopsy was reported as an extrarenal Wilms tumor (ERWT) with triphasic components. Post-chemotherapy, a computed tomography scan revealed a residual tumor for which she underwent partial cystectomy. The diagnosis of ERWT was confirmed. She received adjuvant chemotherapy and remained well at the 9^th month post completion of chemotherapy. The primary bladder WT must be considered in the differential of a small blue round cell tumor at an extrarenal site in the pediatric age group. The diagnosis is especially challenging in small biopsy material, although it has immense significance in management and prognosis.

Keywords: Antineoplastic Agents; Cystectomy; Urinary Bladder; Wilms Tumor.

Figure 1. A – CEMRI with MR urography shows polypoidal, heterogeneous mass over the anterosuperior aspect of the urinary bladder wall. The mass with both endophytic (arrow head) and exophytic (arrow) growth is seen; B, C, and D are photomicrographs of the bladder tumor; B and C – Pretherapy cystoscopy guided biopsy showing triphasic component comprising blastemal (B; H&E, 200X), and epithelial and mesenchymal elements (C; H&E, 200X); D – The blastemal component positive for WT1 immunostain (200X).

Figure 2. A – The partial cystectomy specimen reveals exophytic polypoidal growth; B – The cut surface shows both endophytic and exophytic growth with grey white and firm in appearance. The endophytic component is surrounded by the cystic space containing gel-like material.

Figure 3. Photomicrographs of the partial cystectomy specimen showing: A – a polypoidal mass arising within the lumen. Bladder wall with detrusor muscle can be appreciated (right) (H&E, 40X); B – Biphasic component comprising of glomeruli, tubules, and smooth muscle fibers (H&E, 200X); C – Heterologous mucinous epithelium (H&E, 200X); D – Adipocytic and skeletal muscle differentiation (H&E, 200X).