Lymphatic Malformation (Cystic Hygroma)

Updated: Dec 14, 2020
  • Author: Vijay A Patel, MD; Chief Editor: Ravindhra G Elluru, MD, PhD  more...
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Overview

Background

Lymphangiomas are benign malformations of the lymphatic system. [1] These were first described by Redenbacker in 1828. Lymphangiomas can occur anywhere in the body [2]  and may be broadly characterized as superficial or deep. Within the deep subform, there are macrocystic lymphangiomas and mixed lymphangiomas (see below). Cystic hygromas are macrocystic lymphangiomas (lymphatic malformations [LMs]) that occur in the neck.

Lymphangiomas may also be classified on the basis of their radiographic morphology into three categories: macrocystic (lymphatic structures with diameter >2 cm), microcystic (lymphatic structures with diameter < 2 cm), and mixed. [3]  Treatment varies according to morphology, with each form posing unique management challenges.

The World Health Organization (WHO) recognizes three types of lymphangiomas: capillary, cavernous, and cystic. The first term is a synonym for microcystic lymphangioma, and the second and third are macrocystic lymphangiomas.

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Pathophysiology

LMs are thought to arise from the following:

  • Sequestration of lymphatic tissue from lymphatic sacs during development
  • Failure of these tissues to communicate with the lymphatic or venous system
  • Tissue dilation resulting in the cystic morphology [4]

These lymphatic rests can penetrate adjacent structures or dissect along fascial planes and eventually become canalized. These spaces retain their secretions and develop cystic components, given the lack of a venous outflow tract. The nature of the surrounding tissue determines whether the lymphangioma is capillary, cavernous, or cystic.

LMs tend to form in loose areolar tissue, whereas capillary and cavernous forms of lymphangiomas tend to form in muscle. Studies using cell proliferation markers have demonstrated that lymphangioma enlargement is related more to engorgement than to actual cell proliferation. Molecular studies suggest that vascular endothelial growth factor C (VEGF-C) and its receptors may play an important role in the development of LMs. [5]

In addition to congenital development, LMs can be acquired. They can arise from trauma (including surgery), inflammation, or lymphatic drainage pathway obstruction.

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Etiology

Karyotypic abnormalities are present in 25-70% of children with LMs. LM tends to be more common in patients with Turner syndrome, Down syndrome, Klinefelter syndrome, and trisomy 18 as well as 13, though these are not considered to be causative.

In addition, several nonchromosomal disorders, including Noonan syndrome, Fryns syndrome, multiple pterygium syndrome, and achondroplasia, are associated with an increased incidence of LM. Intrauterine alcohol exposure has been associated with the development of LM. Dissolution of bone caused by either LM or hemangiomas is termed Gorham-Stout syndrome. [1, 4]

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Epidemiology

The incidence of LM is estimated to be 1 per 6000-16,000 live births.

Most LMs (50-65%) are evident at birth, and 80-90% are present by age 2 years. Some authors believe that all LMs are present at birth, even though they may not have fully manifested at that time. [6]  LM can be visualized with abdominal ultrasonography (US) by 10 weeks' gestation, though transvaginal US provides superior detail. Fast-spin magnetic resonance imaging (MRI) can also be used to determine the extent of fetal LM. Elevated alpha fetoprotein levels in amniocentesis fluid have been reported in pregnancies with LM.

The sex distribution is equal. Most series report no racial predominance, though a decreased incidence in African Americans has been described.

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Prognosis

In some series, the reported mortality has been as high as 2-6%, usually secondary to pneumoniabronchiectasis, and airway compromise. Obviously, this figure is pertinent in the larger lesions.

As would be expected, morbidity depends on the anatomic location of the LM. In general, morbidity is related to cosmetic disfigurement and impingement on other critical structures, such as nerves, vessels, and laryngotracheal complex.

Unlike hemangiomas, LMs do not commonly resolve spontaneously. Recurrence is rare when all gross disease is removed. If residual tissue is left behind, the expected recurrence rate is approximately 15%.

In antenatal cystic hygroma (CH), diagnosis after 30 weeks' gestation is considered a positive prognosticator. A study by Lejeunesse et al involving 69 fetuses with LMs diagnosed in the first trimester suggested that the following were predictors of a poor outcome [7] :

  • Nuchal thickness greater than 6.0-6.5 mm
  • Presence of hydrops fetalis, abnormalities on US, or both
  • Fetal karyotypic abnormalities, evolution of LM on US, or both

A study by Sanhal et al found that fetuses with septated LMs had poor perinatal outcomes. [8]

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