**Core Concept**
Wilm's tumor, also known as nephroblastoma, is a type of kidney cancer that primarily affects children. It is the most common type of renal malignancy in pediatric patients. Understanding the characteristics and behavior of Wilm's tumor is crucial for accurate diagnosis and treatment.

**Why the Correct Answer is Right**
Wilm's tumor typically spreads through the bloodstream rather than the lymphatic system. The cancer cells from the primary tumor can break away and metastasize to other parts of the body, such as the lungs, liver, or bones, via the bloodstream. This hematogenous spread is a hallmark of Wilm's tumor and is responsible for its poor prognosis if left untreated. The lymphatic system plays a minimal role in the spread of this disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true as Wilm's tumor typically presents before the age of 5 years, with a peak incidence around 3 years of age.
**Option B:** This statement is also true as Wilm's tumor often presents as an abdominal mass, which may be discovered during a routine examination or as an incidental finding on imaging studies.
**Option D:** This statement is true as Wilm's tumor is highly responsive to treatment, particularly with a combination of surgery, chemotherapy, and radiation therapy. With modern treatment protocols, the cure rate for Wilm's tumor is excellent, especially in patients with localized disease.

**Clinical Pearl / High-Yield Fact**
A classic clinical correlation for Wilm's tumor is the presence of a triad of symptoms: abdominal mass, hypertension, and hematuria. However, this triad is present in only a small percentage of patients, and the diagnosis is often made incidentally on imaging studies.

**✓ Correct Answer: C. Spreads mostly by lymphatics**