Cystic hygroma (lymphatic malformation) is a benign, multiloculated cystic lesion arising from congenital lymphatic system developmental anomaly. Dilated lymphatic spaces form as a result of lymphatic channels failing to drain into jugular lymphatic sacs. It most commonly locates in the posterior cervical triangle and axilla (75% head-neck, 20% axilla). Typically diagnosed at birth or within the first 2 years; 50% present at birth, 90% before age 2. Frequently detected on prenatal ultrasound and has strong association with chromosomal anomalies (Turner syndrome 45,X; trisomy 21, 18, 13) — particularly large bilateral cervical cystic hygroma is an important indicator of fetal aneuploidy. Ultrasonography is the primary diagnostic modality; typically appears as a thin-walled, multiloculated, anechoic-hypoechoic cystic mass without internal flow. MRI best evaluates anatomical relationships, extent, and surgical planning. Treatment options include surgical excision, sclerotherapy (OK-432/bleomycin), or combination therapy.
Age Range
0-5
Peak Age
-
Gender
Equal
Prevalence
Uncommon
Cystic hygroma results from developmental failure of the embryonic lymphatic system. In normal development, primitive lymphatic sacs (jugular, retroperitoneal, cisterna chyli) connect to the venous system through draining channels. When this connection fails to establish, lymphatic sacs dilate forming dilated, cyst-like spaces. Histologically, cystic spaces are seen lined by single-layered flat endothelial cells (lymphatic endothelium — PROX1 and D2-40/podoplanin positive), containing clear serous fluid. Multiloculation results from multiple dilated lymphatic channels coexisting — each cyst is separated by thin fibrous septa. Thin vessels may be present within septa and bleeding from these vessels can cause hemorrhagic content. The anechoic appearance on ultrasound results from clear serous fluid being acoustically equivalent to water — no particles other than water are present in the fluid so there are no reflectors to generate echoes. Absence of internal flow (Doppler negative) reflects that the cystic spaces are not vascular — they are endothelium-lined lymphatic spaces. The mechanism of strong association with Turner syndrome (45,X) is that lymphatic endothelial cells are affected by X-chromosome genes (particularly VEGFR-3 signaling pathway) — monosomy X disrupts lymphatic development causing cystic hygroma formation. Therefore, chromosomal analysis (amniocentesis or chorionic villus biopsy) is indicated when prenatal cystic hygroma is detected.
Cystic hygroma is transillumination-positive on clinical examination — when a light source is placed behind the mass, light passes through it (light does not pass through solid masses). The ultrasound equivalent of this finding is the mass being entirely cystic, anechoic, with posterior acoustic enhancement and containing no solid component. Posterior acoustic enhancement occurs because fluid transmits ultrasound waves without absorbing them, causing more echoes to return from tissue behind the mass — the sonographic equivalent of transillumination.
Ultrasound demonstrates a thin-walled, multiloculated cystic mass. Cystic components are generally anechoic (clear serous fluid) but internal echoes may be seen in case of hemorrhage or infection. Septa are thin and regular; thick or irregular septa suggest complicated hygroma or infection. Cysts are of variable size — ranging from a few mm to several cm. The lesion is generally compressible (changes shape with transducer pressure). No intracystic flow is seen on Doppler; minimal vascularity may be observed within septa but solid component and significant vascularity are not expected.
Report Sentence
A thin-walled, multiloculated, anechoic cystic mass is seen in the posterior cervical triangle/axilla without internal flow on Doppler; findings are consistent with cystic hygroma (lymphatic malformation).
Prenatal ultrasound reveals bilateral, multiloculated cystic mass in the fetal neck region. Increased nuchal translucency (NT >3.5 mm) may accompany. Large cystic hygroma may be seen with fetal hydrops (skin edema, ascites, pleural/pericardial effusion). These findings seriously increase chromosomal anomaly risk: Turner syndrome (50%), trisomy 21 (15-20%), trisomy 18 (10%), trisomy 13 (5%). Even in cases with normal karyotype, prognostic significance exists — prognosis is seriously poor in the presence of fetal hydrops.
Report Sentence
Bilateral multiloculated cystic mass + increased nuchal translucency is seen in the fetal neck region on prenatal ultrasound; consistent with cystic hygroma and genetic evaluation for chromosomal anomaly is recommended.
On T2-weighted MRI, cystic hygroma appears as a markedly hyperintense multiloculated cystic lesion. Cystic components show homogeneous high T2 signal (clear serous fluid). Septa appear as hypointense thin lines on T2. Fluid-fluid levels or heterogeneous signal may be seen if hemorrhage is present. MRI evaluates the anatomical extent of the lesion, relationships with adjacent vascular and neural structures, and surgical resectability. MRI also shows the proportion of microcystic (capillary lymphangioma) and macrocystic (cystic hygroma) components — this affects treatment selection.
Report Sentence
On T2-weighted MRI, a markedly hyperintense, multiloculated cystic lesion is seen with thin septa; findings are consistent with macrocystic lymphatic malformation (cystic hygroma).
On T1-weighted images, cystic hygroma generally shows hypointense signal (clear serous fluid). If hemorrhage is present, components showing hyperintense signal on T1 may be seen — subacute hemorrhage shows T1 shortening due to methemoglobin content. On contrast-enhanced T1 images, septa show thin enhancement but cystic components do not enhance. Absence of a solid enhancing component is an important feature distinguishing cystic hygroma from solid tumors.
Report Sentence
The cystic lesion shows hypointense signal on T1-weighted images with thin enhancement only in septa on contrast-enhanced series; no solid component is seen.
CT demonstrates a water-density (0-20 HU) multiloculated cystic mass. Septa are thin and show mild enhancement after contrast. Cystic components do not enhance. Density may increase with hemorrhage (30-60 HU). CT evaluates additional findings such as bone erosion or calcification. Cystic hygroma generally does not cause bone erosion — this is a distinguishing feature from malignant tumors. Lesion borders are generally well-defined and sharp, though borders may become blurry if infiltrative (microcystic) component is present.
Report Sentence
A water-density multiloculated cystic mass is seen in the neck/axilla on CT with thin septa showing mild enhancement; consistent with cystic hygroma.
Criteria
Cyst diameter >2 cm, few large cystic spaces, thin septa
Distinct Features
Responds well to sclerotherapy, surgical resection also effective, best prognosis, most commonly seen in posterior cervical triangle
Criteria
Cyst diameter <2 cm (usually <1 cm), multiple small cysts, infiltrative growth
Distinct Features
Less responsive to sclerotherapy, surgery difficult (infiltrative), appears more echogenic on US, diffuse T2 hyperintensity on MRI
Criteria
Both macrocystic and microcystic components together in variable proportions
Distinct Features
Treatment strategy determined by dominant component, surgery + sclerotherapy combination may be needed
Distinguishing Feature
Branchial cleft cyst is usually unilocular and located anterior to sternocleidomastoid muscle; cystic hygroma is multiloculated and in posterior triangle; branchial cleft cyst typically presents later
Distinguishing Feature
Thyroglossal duct cyst is located in the midline and related to hyoid bone; cystic hygroma has lateral location; movement with swallowing is specific to thyroglossal cyst
Distinguishing Feature
Dermoid cyst (teratoma) contains solid and cystic components with fat and calcification; cystic hygroma is entirely cystic without fat; internal echoes are more prominent in dermoid
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
6-monthCystic hygroma treatment is determined by lesion size, type (macro/micro/mixed), location, and symptoms. In large macrocystic lesions, sclerotherapy (OK-432/picibanil or bleomycin injection) may be the primary treatment option — success rate 60-80%. Surgical excision is performed for larger lesions near critical structures. In microcystic type, surgery is more difficult (infiltrative growth) and complete resection rate is lower. In prenatally detected cases, chromosomal analysis via amniocentesis is performed first — genetic counseling and family information is needed in aneuploid cases. Even in normal karyotype cases, large cystic hygroma carries airway obstruction risk — EXIT (ex utero intrapartum treatment) procedure may be planned. Postnatal airway management is critical. Recurrence rate is 10-15% with incomplete resection being the most important cause.
Treatment of cystic hygromas includes surgical excision or sclerotherapy (OK-432, bleomycin). Airway compromise requires emergency intervention. When detected prenatally, chromosomal anomaly screening is recommended (Turner syndrome, trisomy). Complete excision can be challenging — recurrence rate is 10-15%.