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ABSTRACT  
The majority of cystic hygromas present in childhood, usually below the age of two years(1). A case report of adult presentation is presented, with discussion of development, presentation, pathology and management of cystic hygroma. 
Keywords: lymphangioma, cystic hygroma, angioma 
 

INTRODUCTION 
Cystic hygroma presents most commonly in the paediatric age-group, with more than 90% with its first presentation below the age of two years(1). There are less than 70 reported cases in adulthood(2). Here, we present a recent case report, followed by discussion on cystic hygroma presenting in adulthood. 
 

CASE REPORT  
A 27-year-old Malay lady presented with a progressively enlarging right neck mass over the past four months. She denied any history of pain, discharge, voice changes, associated upper respiratory tract infection, or any obstructive symptoms caused by the mass like dyspnoea or dysphagia. Physical examination revealed a 10 x 10 cm soft, fluctuant, non-tender right cervical mass in the posterior triangle of the neck. No cervical or axillary lymphadenopathy was noted. Cranial nerves were intact. No neurological deficits were found in the right upper limb. Initial clinical impression was that of a cervical lipoma. 
However, aspiration of the mass revealed straw-coloured fluid, and cytology showed abundant mature lymphocytes with no malignant cells. CT scan of neck was requested, which showed a low-attentuated, well-defined cervical mass posterior to the sternocleidomastoid muscle, which extends inferiorly to the lateral aspect of the right clavicle (Fig 1). 
Surgical excision of the mass revealed a large lymphatic malformation, extending to the supraclavicular fossa but not into the axilla. The supraclavicular nerve was draped over the cystic lesion. Histological examination showed irregularly-shaped cystic spaces with fibrous wall lined by flattened endothelial cells, associated with aggregates of lymphocytes, consistent with the pathology of cavernous lymphangioma (cystic hygroma). 
Last follow-up after 2 weeks was uneventful. 

DISCUSSION  
Lymphangioma is a proliferation of lymphatic tissue. It has classically been divided into three different types(3): 
(a)  Simple (capillary) lymphangioma 
 Its pathology is usually a network of endothelium-lined lymphatic channels in subcutaneous spaces, in the absence of any red blood cells. It is usually benign. 
b)  Cavernous lymphangioma (Cystic hygroma) 
 The pathology is a benign lymphatic tumour with cavernous lymphatic spaces. It is not encapsulated, may be large enough to cause obstructive symptoms, commonly occurring in childhood, which may cause difficulty in complete surgical removal. 
c)  Lymphangiosarcoma (lymphoedema-associated angiosarcoma) 
 A rare tumour developed after prolonged lymphatic obstruction with lymphoedema, especially after radical mastectomy for carcinoma of the breast. It is lined by anaplastic endothelial cells. 

The majority of lymphangiomas occur in the head and neck region. It is known that all the lymph vessels of this region drain into the deep cervical terminal group, which is related to the carotid sheath, and efferents subsequently forming the jugular trunk(4). Hence, any developmental abnormalities of this lymphatic system will result in cervical lymphangioma. 
Review of the embryology of the lymphatic system showed two major theories being proposed. The centrifugal theory proposed by Sabin(5) suggested that the outgrowth of venous system will become the lymphatic system. Venous buds are sequested into five sacs in the first 2 months of embryonic development - the paired jugular and posterior sacs, and a single retroperitoneal sac. From these structures, endothelial channels proliferate centrifugally. 
The centripetal theory(6) believed in mesenchymal slits appearing in the venous plexus reticulum, and further coalescence of these structures will form lymphatic channels. However, the centrifugal theory is more acceptable because it explains the commoner location of lymphangiomas being near primitive sacs, especially in the neck region. 
From review of literature, majority of clinical presentations in adulthood are typically an asymptomatic mass in the posterior triangle of the neck, often growing rapidly over a period of weeks(2). A study of 32 patients in Mayo Clinic showed that 97% presented with enlarging neck mass, and within six months, in 53% of the cases(7). There was no history of preceding neck trauma, but a few were noted to be associated with an upper respiratory tract infection. Lesions are usually transilluminant, non-tender, fluctuant and fixed to deep tissues, similar to paediatric presentation. However, dysphagia or respiratory symptoms are uncommon in adults(2), unless occurring in the midline or submental area, as compared to children. Most often, without the benefit of imaging studies, those in the neck are misdiagnosed pre-operatively as branchial cysts(8), lipoma, or lymphadenopathy(7). 
The usual histopathological examinations of cystic hygroma show smooth cystic masses, sometimes multi-lobulated, lined by a single layer of flattened endothelium. The masses include buds of lymphangiomatous tissue and collections of lymphocytes(9). 
 

TREATMENT AND MANAGEMENT 
Sclerosing agents and radiation treatment had largely been abandoned due to their potential side effects. Aspiration may result in rapid re-accummulation, and since lesions are sometimes multi-loculated, complete aspiration is unlikely to be successful(2). The most acceptable form of management is complete surgical excision of the lesion. This is successful especially if preceded by pre-operative radiographic imaging by CT scan to define the extent of the lesion, and its surrounding vital structures. 
Recurrence after surgical resection may appear up to 15% of patients, especially with incomplete removal of the lesion. Such recurrence appears to happen within one year, and is associated with an upper respiratory tract infection(8). 
It is hence recommended that post-surgical follow-up of patient should be up to 2 years to detect any recurrence. 
 

CONCUSION 
Cystic hygroma is an uncommon differential diagnosis of a rapidly enlarging neck mass in adulthood. It may be possible that this congenital abnormality of the lymphatic channel has been present since childhood, and is triggered by an unknown mechanism in its rapid enlargement in adulthood, leading to its presentation to the clinicians.