risk stratification

A 2-year-old child is evaluated for a 6-week history of increasing abdominal girth, decreased appetite, and occasional bone pain. Physical examination reveals a large, firm, irregular mass in the upper abdomen that appears fixed and crosses the midline. Vital signs are within normal limits for age. Initial investigations show mild anaemia and elevated serum lactate dehydrogenase. An abdominal CT scan is performed (image provided). Given the findings demonstrated in the image and the clinical context, which of the following molecular or genetic analyses is considered a critical determinant of risk stratification and influences treatment intensity for the most likely underlying malignancy?