DOI: https://doi.org/10.36347/sjmcr.2025.v13i12.018

Pages: 2964-2966

Cystic partially differentiated nephroblastoma is a rare cystic variant of Wilms tumor characterized by a multiloculated architecture with cystic septa containing blastemal, epithelial, and stromal components. Its distinction from multilocular cystic nephroma may be challenging, particularly after neoadjuvant chemotherapy, which can modify histological features. We report the case of a 4-year-old girl treated with preoperative chemotherapy according to the SIOP protocol. Nephrectomy revealed a well-circumscribed, encapsulated, multiloculated cystic renal mass measuring 7.5 cm, with an estimated tumor volume reduction of 15 percent. Histological examination showed preserved triphasic differentiation, with predominant mesenchymal stroma, 20 percent epithelial differentiation, and focal blastemal remnants comprising 10 percent of the tumor. Immunohistochemistry demonstrated strong nuclear WT1 expression in blastemal and epithelial components, cytoplasmic vimentin positivity, and nuclear PAX8 expression in epithelial structures. This case highlights the importance of identifying residual triphasic differentiation and using immunohistochemistry to distinguish cystic partially differentiated nephroblastoma from cystic nephroma, thereby ensuring accurate diagnosis and appropriate management