Paediatric Radiology

A 5-day-old child presents with a neck swelling. A CT scan of the neck is requested for. 
What is the diagnosis?

__________SCROLL FOR ANSWER__________

Imaging Findings reveal a low-attenuation mass lesion in the cervical region, which was noted extending to the axilla.

Diagnosis
Cystic Hygroma

Discussion

Introduction
This malformation is commonly localized in the nuchal region (75% of cases). An additional 20% are found in the axilla, while the remaining 5% are found in the mediastinum, retroperitoneum, abdominal viscera, groin, bones and scrotum.

Pathogenesis
There are at least three theories to explain the origin of cystic hygroma.
The first theory suggests that an early jugular-lymphatic obstructive sequence could cause hydrops fetalis, pterigium colli and cystic hygroma. This obstruction impedes communication between the jugular lymphatic sacs and the internal jugular vein.

Some believe cystic hygroma is caused by an abnormal embryonic sequestration of lymphatic tissue and its subsequent failure to join normal lymphatic channels, while a third theory suggests that abnormal budding of the lymphatics occurs between the sixth and ninth weeks of gestation. These then canalize to form lymph-filled cysts.

 Of these three theories, the first seems the most likely. However, the other two theories could be applied to noncervical lymph­angyomatosis.

Types
Lymphangiomas are made up of lymphatic vessels and are, fundamentally, endothelial cells limiting spaces and supporting connective tissue. There are three groups:

 simple lymphangioma, formed by lymphatic capillaries;

 cavernous lymphangioma, formed by bigger lymphatic vessels with a fibrous adventitia;

 cystic lymphangioma, commonly called hygroma, formed by multiple cysts ranging from a few millimeters to several centimeters in size. 

No communication exists between the lymphatic system and a cystic hygroma. Cystic hygromas have a predilection for local infiltration of the dermis, subcutaneous tissue, and soft tissue, and occasionally they are widespread.

 About 50% of these are present at birth, and up to 90% become evident by two years of age. The incidence of cystic hygroma is approximately 1.6:10,000 pregnancies or 0.8% of pregnancies at risk for a structural anomaly^.

Associated anomalies
Although the cystic hygroma may be isolated, in many cases it is associated with hydrops fetalis. Chromosomal defects, particularly monosomy X (Turner's syndrome) and a wide variety of anatomic abnormalities (Table 1) are found in more than 80% of the fetuses. 

Presentation
In most series, the head and neck are the most common sites followed by the trunk, axilla, and extremities. In the head, the oral cavity and face area are the most common sites. In the neck, the posterior triangle is often quoted as the most common site. However, many series have reported no difference between the anterior and posterior triangles. There does seem to be a predominance of right sided lesions. Laryngeal involvement is not uncommon.

The site of the lesion determines the symptomology. Many patients have no symptoms other than a soft tumor mass. Oral cavity and laryngeal involvement can produce stridor, dyspnea, and feeding difficulties.

Diagnosis in the case of large cervical LM is straightforward. The mass is soft, flaccid, fluctuant, with a multilobulated consistency. Imaging studies such as USG, CT, and MRI can be useful in treatment planning. In particular, CT and MRI are most useful in determining proximity to vital structures and mediastinal involvement preoperatively.

Differential Diagnosis
The differential diagnosis includes branchial cleft cyst, thyroglossal duct cyst, congenital retention cysts, dermal cyst, foregut cysts, deep hemangiomas, lymphadenitis, lipoma, malignancy and ranula.

Net Links

1    2