Lymphatic Malformations

Epidemiology

Lymphatic malformation (LM) is the current term used to describe lymphangiomas. Mulliken and Glowacki recommend that the suffix oma only be used in lesions that exhibit cellular proliferation, such as a hemangioma. LM is a congenital lesion that results from a defect in embryogenesis of the lymphatic system. Such lesions occur in equal frequency in males and females. They most commonly present in newborn children, with 65% of lesions noted at birth, 80% present at 1 year, and 90% present by 2 years of age. Ten percent of LMs may initially present in adulthood. LMs may be localized or associated with a generalized malformation of the lymphatic system. Advanced generalized disorders may be seen as diffuse lymphangiectasis in utero and are incompatible with life. LM has been associated with a number of syndromes, the most common being Turner’s syndrome. Other syndromes include Noonan’s syndrome, fetal alcohol syndrome, familial pterygium syndrome, distichiasis–lymphedema syndrome, and various chromosomal aneuploidies.

Embryology

LM is thought to arise from a defect in the normal drainage of the lymphatic channels into the venous system. The result is a progressive enlargement of the isolated lymphatic spaces due to the continued secretion of lymph. There are several proposed explanations for this malformation. The malformation may be due to a portion of the lymphatic network that fails to reestablish a communication with the venous system and is sequestered early in embryogenesis. Early malformations involving the more primitive jugular, subclavian, and axillary sac are thought to result in the formation of the larger cystic hygromas. These lesions occur in soft areolar tissues in areas with wide fascial planes, with the result being sharply demarcated round or oval lesions. Lesions that have smaller cystic spaces and are more diffuse and infiltrative are felt to occur later in embryogenesis. These malformations have time to grow distally along narrower fascial planes and insinuate themselves along vessels and nerve trunks. This probably results in the mixed malformations described by Mulliken and Glowacki such as lymphaticovenous and lymphaticocapillary malformations. Thus LMs that occur in the cheeks, lips, and tongue tend to contain more of an angiomatous component.

Pathology

Pathologically, LMs have been categorized in the past based on the size of the anomalous lymphatic space. It should be noted that lymphatic malformation has replaced terms such as cavernous lymphangioma and capillary lymphangioma, which probably refer to the “mixed” lymphatic malformations described by Mulliken and Glowacki. We present the older terminology below for historical consistency.

Cystic hygroma is the most common form and consists of a honeycomb of very large dilated lymphatic spaces lined by a single layer of flat endothelium. These lesions are often solitary and occur in the presence of an otherwise normal lymphatic system. Seventy-five percent of these lesions occur in the neck. These lesions have a predilection for the posterior compartment of the neck.