Cystic hygroma

General features:
Most common lymphangioma
5% of benign tumors of infancy and childhood
Nearly 90% are diagnosed by 2 years of age
Lymphangioma similar to cavernous lymphangioma, capillary lymphangioma and vasculolymphatic malformation

Embryology:
From early sequestration of embryonic lymphatic channels in developing jugular lymph sac pair
Involution of cystic hygroma in utero leads to web neck in Turner syndrome?

Clinical features:
Nearly 80% involve neck and lower face
Most are asymptomatic
Present as painless, soft or firm neck mass
Variable in size

Location:
Most are in posterior space
2nd most common site is oral cavity
Rare in adults, but commonly seen in sublingual, submandibular, parotid spaces
20% occur in axialla, 5% in mediastinum
Rare in colon, spleen, liver, kidneys, scrotum, skeleton
3%–10% of cervical ones extend into mediastinum

Pathology:
Multiple dilated cystic spaces separated by minimal intervening stroma.
Most contain chylous fluid
Lined by endothelial cells

Complications:
Very large ones may compress airways, leading to suddden death
Sudden increase in size due to hemorrhage, trauma or infection
Facial nerve paralysis
Dysphagia
Chylothorax
Chylopericardium

Imaging:
Commonly diagnosed antenatally
Multilocular cystic mass with septa of variable thickness in posterior neck
Infiltrative and do not respoect fascial planes
May cross midline

US:
Fluid-fluid levels may be seen due to hemorrhage

CT:
Illdefined, multiloculated, homogenously low attenuation lesion centered in posterior triangle or submandibular space

MR:
May show high signal on T1 due to hemorrhage or lipid content
Fluid-fluid level may be seen due to hemorrhage

References:
1. Koeller KK et al. Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation. Radiographics. 1999;19:121-146