Solution to Unknown Case # 11 – Differential Diagnosis of a Cystic Pediatric Neck Mass

History: 5 year old male with a midline neck mass. 

Lymphatic malformation (cystic hygroma): Ultrasound of the midline neck shows a predominately hypoechoic mass with multiple thin septations, which is consistent with a lymphatic malformation, also called a cystic hygroma.

This is the appearance of a lymphatic malformation, which use to be termed “cystic hygroma.” A lymphatic malformation is a congenital malformation of lymph channels which collect into embryonic lymphatic sacs. They can virtually be found in any head and neck location, and are characteristically trans-spatial, such as both infra and suprahyoid. They can be unilocular or multilocular (septated) as seen on the image above, and are mostly anechoic to hypoechoic. A fluid level in a lymphatic malformation suggests prior hemorrhage.

The differential diagnosis for cystic neck masses in the pediatric population is as follows:

1. Infected (also called suppurative) lymph node.

2. Abscess

3. Thyroglossal duct cyst

4. Lymphatic malformation

5. Ranula

6. Second branchial cleft cyst (which is usually lateral and not midline)

7. Dermoid and epidermoid cysts are more rare considerations