Abdominal ultra-sonography in a 3 year old boy show a solid circumscribed hypoechnoic renal mass. Most likely diagnosis is -

Amongst the given options only Wilms tumor is common at 3 years of age :-  Wilm's tumor                  → young children (mean 3 years) Mesoblastic nephroma     → < 1 year Renal cell carcinoma        → > 40 years Oncocytoma                    → 25-95 years (mean 65)