Address correspondence to Thangam R Varma, PhD, FRCS, FRCOG, St George"s Hospital & Medical School, Cranmer Terrace, London, SW17 ORE, United Kingdom, Ph: 44-81-672-9944, Fax: 44-81-767-9585.

Synonyms: Lymphangioma, jugular lymphatic obstructive sequence, hygroma colli cysticum.

Definition: The term hygroma means moist tumor. Cystic hygroma colli are anomalies of the lymphatic system characterized by single or multiple cysts within the soft tissue, usually involving the neck. It contains a clear or cloudy fluid-like lymph.

Prevalence: The incidence of cystic hygroma colli is not well defined. Reports range from 1.7:10,000 pregnancies to 0.83% of pregnancies at risk for having a structural anomaly^1-4. Byrne et al.¹ reported that cystic hygroma colli was found in 0.5% of spontaneously aborted fetuses with crown-lump length greater than 30mm.

Etiology: In the embryo, the lymphatic system drains into the jugular lymphatic sac. A communication between this primitive structure and the jugular vein is formed at 40 days of gestation (conceptional age). Failure of development of this communication results in lymphatic stasis. Dilatation of the lymphatic channels leads to the clinical manifestations of the jugular lymphatic obstructive sequence⁵. Dilatation of the jugular lymphatic sac leads to the formation of a cystic structure in the cervical region.

Pathology: Over-distention of the jugular lymphatic sacs that are located in both sides of the neck results in the formation of a cystic structure that is usually partitioned by a thick fibrous band corresponding to the nuchal ligament. Within the cystic structure, thinner septa are seen and are thought to derive from either fibrous structure of the neck or deposits of fibrin⁶.

Associated anomalies: Cystic hygroma colli are very frequently associated with chromosomal aberrations and consequently with a wide variety of anatomic defects.

Differential diagnosis: Cervical meningocele, cephaloceles, neck tumors, subcutaneous edema, goiter, cystic teratoma and heman­gioma.

Prognosis: The mortality rate of cystic hygroma colli with hydrops is 100%. In many cases, intrauterine demise occurs within the first two trimesters of pregnancy.

Recurrence risk: The recurrence risk for aneuploidy is low, but cystic hygroma colli with a normal karyotype may be inherited as an autosomal recessive trait with 25% recurrence.

Management: Standard obstetrical care.

MESH Lymphangioma-diagnosis; Thoracic-Neoplasm,-congenital BDE 3284 MIM 257350 ICD9 2281 CDC 239.200 (neck location), see also 228.100 for non-neck location (Soft tissue anomalies)

Introduction

Cystic hygroma colli probably represent the most common cause for a neck mass detected prenatally. Other neck masses detectable ultrasonically include cervical meningomyelocele, heman­gioma, teratoma, goiter, sarcoma, and metastatic adenopathy. Occasionally, a large cephalocele may mimic a neck mass. In most of these rare cases, polyhydramnios, hydrops fetalis, or other clinical features signal a careful search of the fetal neck.

Even when the ultrasonographer cannot predict the exact histology of a neck mass, detection of a tumor permits optimal perinatal management since large but histologically benign tumors may cause dystocia or obstruct the upper respiratory tract and necessitate emergency intubation at birth. In other cases, detection of a neck abnormality (ie, cystic hygroma colli) may indicate a high likelihood of chromosomal anomaly or biochemical disturbance (i.e. goiter). Attempts at definitive antenatal diagnosis of fetal neck abnormalities, therefore, are by no means merely a mental exercise but provides useful clinical information.

Polyhydramnios with excessive fetal movements, extreme maternal obesity, or flexion of the neck with fetal crowding during the third trimester may limit visualization of the neck in approximately 5% of cases⁷.

The most useful parameters to assess following detection of a neck abnormality are included in Table 1.

Table 1: Useful parameters to assess neck abnormality.

Review of seven cases

Materials and methods

Seven cases of cystic hygroma colli were diagnosed from January 1985 to December 1991 at St George"s Hospital, London, U.K., using ultrasonic examination. Routine ultrasonic examination was performed on all women who were scheduled to have their babies at St. George"s Hospital between 16 and 20 weeks gestation, to confirm the gestational age, to exclude or confirm multiple pregnancies and to exclude fetal anomalies. The ultrasonic examinations were performed by two obstetricians skilled in the technique and by one skilled senior ultrasonographer. Of the 4760 patients who underwent the examination, seven were found to have a fetus with cystic hygroma colli of varying size. The diagnosis was made before they completed 20 weeks gestation.

The ultrasonic examination was performed using Kretz Combison 320 using a 3.5 MHz sector scanner transducer at a velocity of 1540 meters per second.

Following the ultrasonic diagnosis of cystic hygroma colli, the findings were discussed with the couple, and they were counselled for further assessment using karyotyping following amniocentesis or cordocentesis and for termination of pregnancy.

All seven patients requested for karyotyping and termination of pregnancy. Five of seven had cordocentesis, and two had amniocentesis at 16 weeks gestation. Subsequently, all seven underwent PGE₂ termination of pregnancy without any complication, within 12 hours of initiation of termination. All the seven fetuses had skin biopsy for karyotyping, and they were examined macroscopically by the resident on-call who documented the findings. The fetus was sent for further examination to the Department of Histopathology for the attention of the specialist who examines all the fetuses and infants born dead or who died within four weeks after birth.

Results

The diagnosis of cystic hygroma colli was established by the following criteria:

·         asymmetric, thin-walled multiseptate, cystic masses of the posterolateral aspects of the neck,

·         absence of meningocele, cephalocele, and calvarial defects.

Two of the seven fetuses with cystic hygroma colli had sonographic evidence of ascitis and mild pleural effusion. All the seven fetuses had abnormal karyotyping. Five of the seven (71%) had monosomy X (45X0), one had trisomy 21 and one had trisomy 18. All the seven patients opted for termination of pregnancy. The skin biopsy from all the seven fetuses confirmed the original karyotyping. All the fetuses were examined by the specialist pathologist and confirmed that the seven fetuses had cystic hygroma colli and two had ascitis and mild pleural effusion. But none had any other structural abnormalities. The age of the patients ranged between 24 and 38 years, and the parity ranged between 0 and para 4. Table 2 shows the details of the seven women.

Table 2: Details of the seven women with cystic hygroma colli.

Discussion

The incidence of cystic hygroma colli in the group of 4760 patients who had an ultrasonic examination was approximately 1 in 680. A review of the literature shows that the incidence of cystic hygroma colli ranges from 1 in 6000 to 1 in 120 pregnancies^1-4. Only two of seven (28.5%) had hydrops, whereas Chervenak et al¹¹ and Pearce et al¹² reported that the incidence of hydrops was 76%. However, the hydrops fetalis usually develops towards the end of second trimester or third trimester. All our seven patients had an early diagnosis in early second trimester and had an early termination—hence the reason for the low incidence of hydrops fetalis.

Four of seven (59%) had oligohydramnios, one had polyhydramnios and two had normal amount of amniotic fluid. Chervenak et al¹¹ and Pearce et al¹² reported that 60% of pregnancies with cystic hygroma colli had oligohydramnios.

Five of seven (71%) had mono­somy X (45X0). The others reported an incidence of 45%-50%^9,11,13,17.

None of our seven patients opted to continue with the pregnancies; hence, the outcome of pregnancies with cystic hygroma colli, if continued, could no be assessed. However, in view of the fact they were complicated by the chromosomal analysis, the prognosis would have been poor.

Clinical and pathological findings

Cystic hygroma colli probably results either from abnormal embryonic sequestration of lymphatic tissue or from abnormal budding of lymphatic endothelium between the sixth and ninth week of gestation⁸. Failure of the jugular lymphatic sacs to drain into the internal jugular vein probably results in the dilatation of the lymphatic sacs into cystic spaces and may lead to the jugular lymphatic obstruction sequence and hydrops fetalis⁹. If the connection is formed, the sequence is interrupted and the fluid collections are resorbed. The redundant skin will give rise to webbed neck (pterygium colli), which is typical characteristic of Turner"s syndrome and of many other genetic and nongenetic conditions.

Cystic hygroma occurs in the neck in approximately 80% of cases; it is then termed cystic hygroma colli. It typically involves the posterior and lateral portions of the neck and often occurs bilaterally in an asymmetric fashion, although the left posterior triangle is the most frequent single location postnatally. The size of the lesions may vary greatly from small collections of fluid to enormous cysts that may be larger than the fetal head. In cases of generalized hydrops, pleural effusion, ascitis, and severe skin edema are present.

Associated anomalies

Cystic hygroma colli are frequently found in association with chromosomal anomalies, mainly Turner"s syndrome (50%). Trisomy 21 (6.6%), trisomy 18 (5%), trisomy 13 (3.3%), and 47 XXY (1.6%) were also found associated with cystic hygroma colli. When isolated, this anomaly can be inherited as an autosomal recessive trait¹⁰. Webbed necks or redundant skin are found in genetic and nongenetic syndromes, such as Noonan"s syndrome, familial pterygium colli, and fetal alcohol syndrome.

Cystic hygroma colli often progresses to hydrops fetalis. In four of the largest series reported 59 of 79 (76%) fetuses with cystic hygroma colli had hydrops^9,11,12,13. Oligohydramnios complicates 60% of pregnancies with cystic hygroma colli, whereas polyhydramnios is unusual^11,12. The etiology for oligohydramnios remains conjectural, but it possibly results from fetal hypoperfusion leading to decreased renal output; the polyhydramnios probably represents a manifestation of hydrops rather than esophageal compression.

Cystic hygroma colli has been described in rare cases with cardiac defects, diaphragmatic hernia, or hydronephrosis, and as a manifestation of the Noonan and Roberts syndromes^2,14,15,16.

Approximately 45%-50% of fetuses with cystic hygroma colli have monosomy X^9,11,13,17. Only one of every 150 fetuses with Turner"s syndrome do not undergo a spontaneous abortion¹⁸. Cystic hygroma colli may also occur as a manifestation of other chromosomal anomalies, especially trisomies 21, 18, and 13, which account for 10%-15% of cases with cystic hygroma colli^3,13,15,19. Furthermore, 15%-25% of fetuses with cystic hygroma colli have a normal karyotype, which does not imply good prognosis¹¹.

Risk of recurrence

The risk of recurrence for aneu­ploidy is low, but cystic hygroma colli with a normal karyotype may be inherited as an autosomal recessive trait with 25% recurrence^9,10,13,15.

Biochemical anomalies

Elevated levels of amniotic fluid alpha-fetoprotein occur in 40%-50% of cases with cystic hygroma colli, probably on the basis of (a) sampling the hygroma fluid, (b) transudation of alpha-fetoprotein through the thin membrane covering the cystic hygroma colli, or (c) imminent fetal death.

Concomitant cystic hygroma colli and neural tube defect or an terior abdominal wall defect is rare. Acetylcholinesterase  activity can be absent in amniotic fluid but present in fluid aspirated from the cystic hygroma colli. Measurement of alkaline phosphatase  isoenzyme may distinguish cystic hygroma colli fluid which has no intestinal isoenzyme from amniotic fluid which contains approximately 80% intestinal enzymes during the second trimester²⁰.

Diagnosis

The diagnosis of cystic hygroma colli relies on the demonstration of cystic structures using ultrasonography, usually located in the occipito-cervical region^{3,6,8,9, 11,12,19.21}. Usually it is detected on routine ultrasonic examination during the second trimester²². Although it has been detected as early as 12 weeks" gestation, the mean age of diagnosis is approximately 19 weeks^{9,18,23,24,25}. The finding may regress and disappear later in gestation^26,27.

These lesions have a typical honeycomb appearance due to the presence of multiple septa (fig. 1). Large lesions are usually characterized by a thick septum dividing the cyst along the anteroposterior axis, the sonographic counterpart of the nuchal ligament. The ultrasound of cystic hygroma colli typically shows asymmetric, thin-walled, multiseptate, cystic masses of the posterolateral aspects of the neck (fig. 2), but cystic hygroma colli may localize anteriorly or extend into the axilla or mediastinum (p 2281-1-8). The loculations range in size but in 85% of cases are as large or larger than the head. Identification of the midline septation extending from the posterior neck and representing the nuchal ligament outlined by bilateral cysts constitutes the most characteristic feature for the diagnosis of cystic hygroma colli.

Figure 1: Section showing the large loculated cystic lesion surrounding the anterior aspect of the nuchal region. 

Figure 2: Transverse section of the cranium at the level of the thalami, showing loculated cystic lesions posteriorly.

Differential diagnosis

Fetal neck heman­gioma may produce similar picture but the cysts are thick walled, contain low level echos, and the lesion extend into the thorax and upper abdomen, but their distinction from cystic hygroma colli is quite subtle²⁸.

Occasionally, a cystic hygroma colli may mimic a cervical meningocele or low occipital encephalocele, but identification of the characteristic nuchal ligament in the absence of spinal dysraphism or calvarial defect discriminates cystic hygroma colli from a neural tube defect^12,29.

Other conditions which may potentially mimic a cystic hygroma colli, include a segment of umbilical cord behind the neck, prominent fetal hair, a pocket of amniotic fluid temporarily trapped against the neck and adjacent subchorionic cyst³⁰. Sonographic examination should diagnose cystic hygroma colli reliably and accurately in virtually all cases during the second trimester of pregnancy (Table 3).

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