Anaplastic Wilms’ Tumor Mimicking a Rhabdoid Tumor: A Diagnostic Challenge

Rhabdoid tumor of the kidney (RTK) mimics other renal tumors histologically, but a rhabdoid tumor mimicking an anaplastic Wilms’ tumor has been rarely reported. Wilms’ tumor classically comprises three histological components, including a blastema, epithelium, and stroma. The degree of maturation of these components makes the histological appearance of this tumor unique. Anaplasia is defined by the presence of extreme nuclear and mitotic atypia. Most of these lesions can be differentiated on the basis of light microscopic histological investigations. Herein we report a case of pediatric anaplastic Wilms’ tumor that was difficult to differentiate from a mesenchymal lesion histologically. The application of immunohistochemistry and extensive sampling of the lesion was critical for accurate diagnosis.