**Question:** Following is true about Wilm's tumor, except:

A. It is a common tumor in children.
B. It is a rare tumor in adults.
C. It is a type of leukemia.
D. It is caused by a genetic mutation.

**Core Concept:** Wilm's tumor is a type of kidney cancer that occurs predominantly in children. It originates from the nephron, which is the functional unit of the kidney responsible for filtering blood and producing urine. Wilm's tumor has a specific genetic basis, with mutations in Wilms tumor suppressor genes (WT1, WTX, VHL, and others) being implicated in the development of the tumor.

**Why the Correct Answer is Right:**

Option A is correct because Wilm's tumor is indeed a common tumor in children. In fact, it is the most common kidney tumor in children and accounts for approximately 5-10% of all pediatric renal tumors.

Option B is incorrect because Wilm's tumor is not rare in adults. Although it is more common in children, it can also occur in adults, albeit much less frequently.

Option C is incorrect because Wilm's tumor is not a type of leukemia. Leukemia is a group of blood cancers characterized by excessive production of immature white blood cells, while Wilm's tumor is a renal cancer affecting the nephron.

Option D is correct because, although Wilm's tumor is associated with genetic mutations, it is not solely caused by a single genetic mutation. Mutations in multiple genes, including WT1, WTX, VHL, and others, contribute to the development of Wilm's tumor.

**Why Each Wrong Option is Incorrect:**

Option C (Wilm's tumor is a type of leukemia) is incorrect because Wilm's tumor and leukemia are distinct entities affecting different cell types: Wilm's tumor affects nephrons (renal parenchyma) while leukemia affects the hematopoietic system (blood and bone marrow).

Option A (Wilm's tumor is common in adults) is incorrect because, while Wilm's tumor is rare in adults, it can still occur in adults. However, it is more common in children.

Option B (Wilm's tumor is a single genetic cause) is incorrect because Wilm's tumor is associated with multiple genetic mutations, including WT1, WTX, and VHL mutations. While these mutations can be found in approximately 90% of Wilm's tumor cases, it is not solely caused by a single genetic mutation.

**Clinical Pearls:**

1. Wilm's tumor is a rare kidney tumor in adults.
2. Wilm's tumor is associated with genetic mutations involving multiple genes (WT1, WTX, VHL, etc.) rather than a single genetic cause.
3. Differentiating between Wilm's tumor and leukemia is crucial since they affect different cell types (nephrons vs. hematopoietic cells) and require different diagnostic and therapeutic approaches.