Answer of July 2011

Clinical History:

A 7 years old girl presented with recurrent painless mass over right parotid region.

                                                Contrast CT of the neck  

                                        Pre- and Post-contrast T1W MRI

                                                          T2W MRI

            USG scan of the lesion

Diagnosis:

Lymphangioma

Discussion:

Lymphangioma is a common congenital benign tumour of infancy and childhood, in 80-90% evident by age of 2 which is of the time of greatest lymphatic growth. It is characterized by multilocular thin-walled cysts separated by fibrous tissue, resulted from abnormal budding of lymph vessels (loss of connection of the lymphatic sac with vein) causing obstruction of lymphatic drainage. It can be located in anywhere in developing lymphatic system, most commonly at the posterior triangle of the neck and lower portion of face (75-80%), but can also be found in axilla, mediastinum or retroperitoneum.

Lymphangioma can be associated with chromosomal abnormalities in 60-80% of cases, for example Turner syndrome or trisomies 13, 18, 21 etc. It is also believed to be associated with exposure to teratogens such as fetal alcohol syndrome or aminopterin.

Patient is usually presented with asymptomatic soft or semi-firm mass over the neck, however the mass can show rapid increase in size due to infection or haemorrhage. In some cases, patient may presents with dyspnea or dysphagia if the mass is large enough with encroachment upon trachea, pharynx or esophagus.

On USG scan, there would be thin-walled fluid-filled structures with multiple septa of variable thickness and solid cyst wall components. It can be easily recognized by fluid-fluid levels with layering of haemorrhagic component. CT scan and T2W MRI images also revealed multiloculated septated cystic cavities with fluid-fluid levels. Hyperintense signals on T1W images are likely due to clotted blood or high chylous lipid content. It can be differentiated from other masses by its location and characterized fluid-fluid levels with previous haemorrhage, and be differentiated from haemangioma by lack of contrast enhancement and feeding vessels.