lymphangioma
description
a rare lymph-containing mass, with endothelial-lined spaces which vary in size from channels of capillary dimensions to cysts several centimetres in diameter. these structures are supported by connective tissue stroma of varying thickness, often containing lymph nodes, round cells, and occasional vestiges of smooth muscle and other neighbouring tissues. the cysts are filled with thin, watery, clear or straw-coloured fluid, which may contain monocytes, lymphocytes, and polymorphonuclear cells. lymphangiomas have been classified into three groups: capillary, cavernous and cystic. although they are clinically distinct, there is no sharp dividing line between these, and all three may coexist. there is some evidence that cystic lymphangioma may originally be cavernous. the physical nature of the mass may be determined by the surrounding tissue. cystic lymphangiomas are the most common. 75 to 90% are located in the neck, where they often produce marked distortion of surrounding tissues. the clearly defined tissue planes in the neck, with loose fatty tissues surrounding compact muscles and neurovascular structures, may allow ample expansion of this cystic mass. cystic lymphangiomas are also known as cystic hygromas, however the term lymphangioma is preferred to distinguish this mass from a hygroma, which is the result of jugular lymphatic obstruction, and which has completely separate embryologic, pathologic and clinical features, and associated syndromes. lymphangiomas are probably formed during the process of centrifugal growth and outpouching of the lymphatic primordia as a result of sequestration of lymphatic anlage, which never achieve sufficient anastomosis with larger lymphatic channels. functionally, they exist as a localised area of lymphatic stasis due to blockage of regional lymphatic drainage. the sexes are equally affected.
diagnosis
the masses are often multiloculated, with linear septations of variable thickness. most masses have solid components related to the cyst wall or septa. the solid portions are thus found within and between the cysts. large lesions have ill-defined boundaries and may extend into the axillae or mediastinum. the mass may be located in any area of the neck, although the posterior cervical triangle is most frequently affected. in the anterior triangle, the mouth, tongue and respiratory tract may be infiltrated. large lesions in this location produce marked head hyperextension, causing difficulties in delivery. it may be necessary to carry out elective delivery with ventilation and tracheostomy available. there is generally an absence of other associated abnormalities and lymphedema.
differential diagnosis
a goitre will present as a mainly solid mass, with echolucent areas. cysts of the branchial cleft and thyroglossal duct are embryologic remnants occurring in characteristic locations; the former is found anterolateral to the carotid sheath, and the latter is located in the midline. both tend to be unilocular. teratoma has a complex echo pattern, with solid and cystic components. solid masses of the neck include neuroblastoma, lipoma, salivary gland tumour, and neurofibroma. cystic hygroma is an aetiologically distinct condition resulting from jugular lymphatic obstruction; it is seen as a single or multiloculated fluid-filled cavity, usually in the posterior nuchal region. it lacks a solid component and internal septation is common. a haemangioma is a cystic, solid or mixed mass; occasionally it will be accompanied by multiple internal homogeneous echogenic reflections, representing calcified areas. these are small and widely scattered, unlike the gross calcification of a teratoma. cystic areas may be pulsatile. doppler velocimetry should demonstrate low-resistance blood flow through these cystic areas.
sonographic features
multiple cysts with solid components found both within and between the cysts no association with lymphedema or other abnormalities
associated syndromes
references
allanson je in: human malformations and related anomalies oxford university press: new york, pp 293-304
benacerraf br, frigoletto fd jr prenatal sonographic diagnosis of isolated congenital cystic hygroma, unassociated with lymphedema or other morphologic abnormality j ultrasound med 6: 63-6
thomas rl prenatal diagnosis of giant cystic hygroma: prognosis, counselling, and management; case presentation and review of recent literature prenat diagn 12: 919-923