**Core Concept**
Neuroblastoma is a type of pediatric cancer that arises from the neural crest cells in the adrenal glands or sympathetic nervous system. It is a leading cause of abdominal masses in children and can present with a range of systemic symptoms due to metastasis or paraneoplastic syndromes.

**Why the Correct Answer is Right**
The combination of a palpable abdominal mass, hypertension, sweating, and diarrhea in a 4-year-old child is highly suggestive of neuroblastoma. The abdominal mass is likely due to a primary tumor in the adrenal gland, while the systemic symptoms are thought to be caused by excessive catecholamine production, a common feature of neuroblastoma. The catecholamines, such as adrenaline and noradrenaline, can lead to hypertension, sweating, and diarrhea due to their effects on the sympathetic nervous system.

**Why Each Wrong Option is Incorrect**
**Option B:** Nephroblastoma, also known as Wilms tumor, is a different type of pediatric cancer that arises from the kidneys. While it can present with an abdominal mass, it is less likely to cause systemic symptoms such as hypertension and sweating.

**Option C:** Polycystic kidney disease (PCKD) is a genetic disorder that affects the kidneys, leading to the formation of multiple cysts. It can cause hypertension due to renal impairment, but it is not typically associated with an abdominal mass or systemic symptoms such as sweating and diarrhea.

**Clinical Pearl / High-Yield Fact**
Remember the "4 Ps" of neuroblastoma: **P**alpable abdominal mass, **P**allor, **P**erspiration, and **P**alliative symptoms, which are often due to catecholamine excess.

**Correct Answer:**
✓ Correct Answer: A. Neuroblastoma