A 4-year-old child is brought to the pediatric clinic with complaints of abdominal swelling.
On examination, a firm, non-tender mass is palpable in the right flank.
The child's mother reports no pain or fever but mentions that her child was born with aniridia (genetic eye disorder). Based on these findings, what is the most likely diagnosis?

Choice A rationale

Nephroblastoma, also known as Wilms tumor, is the most common malignant renal tumor in young children, typically presenting between the ages of 3 and 4 years. A firm, non-tender abdominal mass, often in the right flank, is a classic finding. The association with aniridia, a congenital absence of the iris, is a known risk factor for Wilms tumor, occurring in WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and intellectual disability).

Choice B rationale

Neuroblastoma is a cancer that arises from immature nerve cells and can occur in various locations, most commonly the adrenal glands. While it can present with an abdominal mass, it is often associated with other symptoms such as fever, weight loss, and irritability due to catecholamine secretion. It is less specifically linked to aniridia than nephroblastoma.

Choice C rationale

Hepatoblastoma is a rare malignant tumor of the liver that typically presents in children younger than 3 years old. While it causes abdominal swelling due to a liver mass, it is not typically associated with aniridia. Palpation might reveal a mass in the upper right quadrant rather than the flank.

Choice D rationale

Hydronephrosis refers to the swelling of a kidney due to a buildup of urine. While it can cause an abdominal mass, it is often associated with urinary symptoms or pain, which are not reported in this case. Furthermore, it is not a malignancy and has no known association with aniridia.