Extensive chondroid differentiation in a Wilms tumor following chemotherapy: Clinical relevance and implications

Wilms tumor (WT) is the most common childhood tumor of the kidney, which histologically mimics various stages of nephrogenesis. Spectrum of chemotherapy induced histopathological changes has been described in literature, and is one of the most important predictors of disease outcome and survival rates. Extensive chondroid differentiation and absence of necrosis in a post-chemotherapy nephrectomy specimen of a radiologically proven Wilms tumor is an unusual finding. Herein, we present the case of 6-year-old girl from South Africa who received a 10-week course of chemotherapy upon radiological diagnosis of WT, and post-surgery nephrectomy specimen revealed extensive mature cartilage island formation on histology raising diagnostic dilemma. Reporting of such cases is extremely important to recognize tumor morphological heterogeneity, particularly post- chemotherapy, and developing consensus for selecting further treatment and clinical follow-up.