## Core Concept
Cystic hygroma, also known as cystic lymphangioma, is a congenital malformation of the lymphatic system. It typically presents as a fluid-filled sac or cyst, most commonly in the neck region, but can also occur in other parts of the body. This condition arises due to the abnormal development of lymphatic vessels during embryonic development.

## Why the Correct Answer is Right
The correct answer, , highlights a key characteristic of cystic hygroma. Cystic hygromas are indeed congenital malformations that are often detected prenatally or at birth. They are benign lesions that can vary significantly in size and are usually composed of multiple fluid-filled locules. The condition is associated with an abnormal connection between the lymphatic and venous systems, leading to the accumulation of lymphatic fluid within the cyst.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because while cystic hygromas can occur in various locations, they are most commonly associated with the neck.
- **Option B:** This option is incorrect as it does not accurately describe a characteristic feature of cystic hygroma.
- **Option D:** This option is incorrect because cystic hygromas are typically benign and not malignant.

## Clinical Pearl / High-Yield Fact
A key clinical pearl regarding cystic hygroma is that it can be associated with chromosomal abnormalities, such as Turner syndrome, and other congenital anomalies. Therefore, the detection of a cystic hygroma, especially in a fetus, warrants further investigation for potential genetic syndromes.

## Correct Answer Line
**Correct Answer: C.**