Lymphangiomas are rare benign neoplasms believed to be the result of abnormal development of the lymphatic system. They grow very slowly usually localised to one organ, but occasionally involve several organs in one part of the body. In the chest, involvement of the mediastinum, lung, heart, pleura, pericardium, ribs, and vertebrae may be seen in the same patient. Histologically they are made up of spaces lined with endothelium, varying from capillary size to several centimetres in diameter. They contain clear straw coloured fluid occasionally mixed with blood. The spaces are supported by a stroma of variable thickness containing lymphoid tissue. The aetiology is unknown but believed to be a result of congenital malformation of the lymph vessels. Radiation induced cutanous lymphangioma has been described in a patient with breast cancer following mastectomy and radiotherapy.1

Clinically, lymphangiomas are classified into three types:

(1)

Simplex, which is made up of capillary sized thin, walled lymphatic channels. This type usually affects the skin (lymphangioma circumscriptum)

(2)

Cystic lymphangioma (or cystic hygroma): this may range in size from a few millimetres to several centimetres, seen in a young age, commonly in the neck or the axilla

(3)

Cavernosum: this type is made up of dilated lymphatic channels, often with fibrous adventitial coats. This is the type which usually affects organs in the thorax, abdomen, and bones.

Bill and Sumner2 pointed out that the three types may coexist in the same patient. Reports of single organ involvement have been published relating to nearly all organs of the body except for the CNS, which is devoid of lymphatic channels.

In one large series, lymphangioma of the head and neck accounted for nearly 50% of cases in children, while 10% of cases had visceral disease including the thorax.3 Thoracic lymphangioma has been described in all age groups including infants, neonates, and in the stillborn.4 Presenting symptoms are related to pulmonary and/or mediastinal mass, and signs and symptoms of pleural and/or pericardial effusion. Rib or thoracic vertebral bone involvement may present as chronic pain or acute pain in cases of pathological fracture. Bone involvement in the young may result in shortening or deformity of the affected bone.

The plain chest radiograph will reveal either a localised lung lesion, with the solitary type, or diffuse pulmonary involvement with or without thoracic lymphadenopathy. Pleural or pericardial effusion is also common at presentation. Rib or vertebral involvement will be seen as rarefaction of bone, earlier in the course of the disease, or pathological fracture later on.

Parenchymal lung involvement with lymphangiomas has a characteristic computed tomography (CT) scan appearance. This can be seen as lobular or a cystic mass of heterogeneous soft tissue density in the localised type or diffuse involvement, seen as patchy areas of ground glass appearance.

Using conventional and high resolution CT scan (HRCTS), Swensenet al, reporting on eight patients with diffuse disease concluded that the appearance is distinctive and includes diffuse, smooth thickening of interlobular septa and bronchovascular bundles with extensive infiltration of the mediastinal fat and associated perihilar infiltration.5 Pleural thickening and/or effusion were seen in seven of the eight patients. Despite the typical appearance, they stressed the importance of biopsy for a definitive diagnosis. In one study comparing chest x ray with HRCTS of the chest in children with diffuse lung disease, Lynch et alconfirmed the value of HRCTS scan over other conventional radiological methods.6

Any part of the mediastinum can be affected—anterior, middle, posterior, and superior, perhaps with slight prevalence in the anterior part. This will be seen as a well defined multilocular water density mass with or without compression or displacement of nearby structures.7 Shaffer et alpointed out that the magnetic resonance imaging (MRI) findings are not dissimilar from those of a CT scan and may include a cystic component isointense to muscles on T1 weighted images and hyperintense to fat on T2 weighted images.8 Comparing CT, ultrasound, and MRI findings, Pui et al concluded that MRI was more accurate in delineating extent of disease.9 This is important for preoperative surgical planning, and for these cases, coronal and sagittal views will be of great help to the surgeon