**Question:** All are markers of Wilms' tumor except:

A. Alpha-fetoprotein (AFP)
B. Beta-human chorionic gonadotropin (hCG)
C. Carcinoembryonic antigen (CEA)
D. Prostate-specific antigen (PSA)

**Core Concept:** Wilms' tumor is a type of kidney cancer that primarily affects children. Diagnosis of Wilms' tumor often relies on identifying tumor markers in blood or urine samples. Markers are substances produced by, or associated with, the tumor cells.

**Why the Correct Answer is Right:** D. Prostate-specific antigen (PSA) is a marker found in prostate cancer. Since PSA is produced by prostate gland cells, it is not a marker for Wilms' tumor, which affects kidney cells.

**Why Each Wrong Option is Incorrect:**

A. Alpha-fetoprotein (AFP): AFP is produced by yolk sac tumors, which are a type of germ cell tumor. Although AFP can be elevated in some cases of Wilms' tumor, it is not specific to Wilms' tumor alone and can be elevated in other conditions like hydatidiform mole or liver tumors.

B. Beta-human chorionic gonadotropin (hCG): hCG is produced by trophoblastic tumors, which are also a type of germ cell tumor. As with AFP, hCG elevation can be observed in some Wilms' tumor cases, but it lacks specificity for Wilms' tumor diagnosis.

C. Carcinoembryonic antigen (CEA): CEA is primarily produced by gastrointestinal and lung cancers. Although elevated CEA levels have been reported in some cases of Wilms' tumor, it remains a marker for gastrointestinal and lung cancers, making it an unsuitable marker for Wilms' tumor.

**Clinical Pearl:** Proper selection of tumor markers is crucial for accurate diagnosis and management of Wilms' tumor. While elevated AFP and hCG levels can suggest the presence of Wilms' tumor, the diagnosis must be confirmed with other tests and clinical information.

**Correct Answer:** D. Prostate-specific antigen (PSA)

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**Explanation:**

Wilms' tumor is a renal malignancy that primarily affects children, accounting for 10% of all pediatric kidney tumors. Diagnosing Wilms' tumor relies on a combination of clinical history, physical examination, and radiographic findings. While elevated levels of AFP, hCG, CEA, and even B-HCG can suggest Wilms' tumor, these markers are not specific to Wilms' tumor and are also elevated in other conditions like gastrointestinal and lung cancers, hydatidiform mole, or liver tumors.

**Core Concept:** The choice of tumor markers plays a crucial role in differentiating Wilms' tumor from other conditions. Prostate-specific antigen (PSA) is a marker specific to prostate cancer, making it unsuitable for diagnosing Wilms' tumor.

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**Explanation:**

PSA is a marker produced by the prostate gland cells. In contrast to the aforementioned markers, PSA is specific to prostate cancer and