This is a case of Wilm's tumour. Wilms tumor is often associated with mutations in the WT1 gene, CTNNB1 gene, or AMER1 gene CT image shows a mass in the right kidney. Gross nephrectomy specimen shows a Wilms tumor pushing the normal renal parenchyma to the side. HPE image shows the characteristic three components: Malignant small round (blue) cells ~ 2x the size of resting lymphocyte (blastema component) Tubular structures/rosettes (epithelial component) Loose paucicellular stroma with spindle cells (stromal component) The median age at diagnosis of this kidney tumor (see the image below) is approximately 3.5 years. Clinical findings include the following: Asymptomatic abdominal mass (in 80% of children at presentation) Abdominal pain or hematuria (25%) Urinary tract infection and varicocele (less common) Hypeension, gross hematuria, and fever (5-30%) Hypotension, anemia, and fever (from hemorrhage into the tumor; uncommon) Respiratory symptoms related to lung metastases (in patients with advanced disease; rare) Drugs approved for chemotherapy are: - Cyclophosphamide Vincristine Doxorubicin Dactinomycin