Ⅰ. INTRODUCTION

Cystic hygroma is a rare tumor of lymphatic origin, and it represents 1.2% of all tumors (either benign and malignant).¹⁾ The lesions are more common in children, and they comprise 6% of all pediatric soft-tissue tumors.^1,2) This tumor has a rare occurrence in adults, and studies have reported fewer than 150 cases of adult cystic hygroma in the literature.^1,3,4) Cystic hygroma can involve various parts of the body including cervicofacial regions, retroperitoneum, mesentery, groin, extremities, axilla, chest wall, mediastinum, and viscera.^5,7) The head and neck regions account for 40–70% of all the lesions. Despite being a benign neoplasm, the surgical treatment of this tumor is difficult because of its tendency to spread along the vital structures and the subsequent high recurrence rates.^6,7) The purpose of this report is to describe a rare case of cystic hygroma occurring on the left side of the neck in an adult patient.

Ⅱ. CASE REPORT

A 47-year-old male patient with the complaint of a painless, gradually enlarging mass in the left submandibular, neck area was referred to the oral–maxillofacial surgery department. A physical examination revealed swelling, soft palpation, and mobile mass (Fig. 1A, B). Para nasal sinuses computerized tomography scan revealed that a fluid-filled cystic lesion (size: 5.8 × 3.8 × 8 cm), without a soft tissue component or calcification, was located laterally to the left carotid space. The mass was observed to be superiorly extending into the parapharyngeal space and inferiorly extending into the submandibular and anterior cervical spaces (Fig. 1C, D). Under general anesthesia, via apron incision, platysma muscle was elevated and a wide exposure was achieved for neck dissection. The lesion was located between the left sternocleido- mastoid muscle and omohyoid muscle, and closely related to the carotid sheath. The mass was dissected, and SCM was retracted laterally to identify the carotid sheath (Fig. 1E). After blunt dissection, there was a complete resection of the mass. Gross examination revealed that the mass was well-encapsulated and had a macrocystic appearance. (Fig. 1F). Histopathological examination showed that a cystic lesion was made up of dilated lymphatic spaces. These spaces were lined by thin endothelial cells. The scant intervening connective tissue showing few lymphoid aggregates could be observed while separating these spaces (Fig. 1G, H). The final diagnosis was considered as cystic hygroma. After that, the patient did not do a proper followup, and four years later, he was referred to our department again with swelling on the left neck area (Fig. 2A, B). A large cystic lesion (size: 6.5 × 4 × 8 cm) was found around the previous excision site on the left neck. The recurrent cystic mass was mainly located in the submandibular and anterior cervical spaces (Fig. 2C, D). The patient refused surgical treatment, and we decided to perform incisional drainage and aspiration under local anesthesia by using ultrasound. The reddish tissue fluid was detected in aspiration (Fig. 2E). Cytology from the cystic fluid showed the mature lymphocytes (Fig. 2F). Sufficient drainage was performed through the incision site, and the drain was fixed and then sutured. After aspiration, there was an improvement in the symptoms of patient.

Ⅲ. DISCUSSION

Cystic hygroma is an unusual form of lymphangioma, and it is most prevalent in the cervicofacial regions of children.^5,7,8) The chances of developing cystic hygroma are 50–60% and 90% at birth and within two years of age, respectively.⁸⁾ This tumor primarily occurs in adults, and it has been rarely reported. Naidu published a case study with 91 patients along the English literature from 1913 to 2000, with lymphatic malformations in the head and neck regions.⁸⁾ The incidence rates of tumor occurs are 80% and 20% in the cervicofacial and axillary areas, respectively.⁷⁾ The most common site of cystic hygroma is the cervical posterior triangle. However, in case of a large lesion, it extends to the maxillary, mouth floor, and mediastinum.^5,7,9) Lymphangiomas are classified into three types: capillary, cavernous, and cystic. Capillary lymphangioma comprises thin-walled capillary lymphatic vessels, cavernous lymphangioma comprises large, expanded lymphatic vessels, and cystic lymphangiomas or cystic hygroma comprises cysts that are stretched with various endothelial cells ranging from a few millimeters to several centimeters in diameter.¹⁰⁾ The clinical symptoms of cystic hygroma are seen as soft, mobile masses and usually asymptomatic; however, these lesions can get infected due to the seedling of microorganisms from a respiratory tract infection.⁷⁾ Sometimes, cystic hygroma turns into an abscess, which needs to be drained or be treated with antibiotics. The other most frequently reported problem is spontaneous bleeding in the cysts.⁷⁾ On aspiration, they yield hemorrhagic fluid. Surgical intervention may be required in the case of spontaneous bleeding of cystic hygroma of neck area.¹¹⁾

The diagnostic imaging study showed cystic hygroma as the large, cystic masses. Ultrasound is used as the first choice of diagnostic method and can classify the subtype of cystic hygroma while assessing the size of the lesion. CT and magnetic resonance imaging scans can assess the features of the lesion and the involvement of critical and vital structures.¹²⁾

Differential diagnosis of cystic hygroma in adults includes branchial cleft cyst, hemangioma, abscess, lymphoma, hamartoma, thyroid mass, thyroglossal duct cyst, dermoid cyst, metastatic disease, or other tumors.

The histopathological findings of cystic hygroma indicate that several cystic ducts extending into a single line of endothelial cells are supported by the connective tissue. The size of each cyst cavity varies from 1 mm to 5 cm or more, and each cyst cavity contains a serous clear straw- colored liquid and, in case of infection, purulent and hemorrhagic liquid.⁹⁾

The most preferred treatment for cystic hygroma is a complete surgical excision. When the lesions have infiltrated the adjacent vital structures of the affected region, various treatments such as simple drainage, aspiration, radiation, laser excision, sclerotherapy, radiofrequency ablation, and cauterization are attempted.⁷⁾ However, the surgical excision of cystic hygroma, involving vital structures, is not easy. It has possible complications such as injury to the facial artery, facial nerve, major vessels, and incomplete excision in case of infiltration to the surrounding vital structures. In about 20% of cases, there is a recurrence even after the complete excision of the lesions.^7,13-15) Aspiration of the lesion can be performed as a temporary treatment to decrease the size of the lesion; however, it can cause the lesion to be infected.

In conclusion, cystic hygroma occurs mostly in young children, but is rarely found in adults. Differential diagnosis of cystic hygroma is very important, and complete surgical resection is recommended, but it can be difficult to remove the tumor around the vital structures. In this case, other treatments should be considered. It is difficult to completely remove the lesion; therefore, it has a high recurrence rate and requires careful follow-up.