Teratomas are germ cell tumors that originate from totipotential cells and are composed of tissues arising from more than one germ cell layer (1). Teratomas are usually located in the sacrococcygeal region, though they also occur in descending order in ovaries, testes, anterior mediastinum, retroperitoneum, and finally the head and neck, which in total account for less than 5% of cases (2345). Although mediastinal teratomas are the most common extragonadal germ cell tumors (4), they rarely extend to the head and neck regions. To the best of our knowledge, only one case of mediastinal teratoma presenting as a cystic neck mass has been reported (6). Here, we report a rare case of anterior mediastinal teratoma extending to the anterior neck that resulted in a cystic neck mass.

A 38-year-old man presented with right anterior neck swelling of five months duration. He had complained of a palpable lower cervical neck mass a few months previously, but at the time a thyroid mass was suspected. Fine needle aspiration was performed, but revealed only a colloid nodule. Subsequently, the mass, which was located in right paratracheal area, increased in size without associated focal or systemic inflammatory manifestations. The patient remained asymptomatic with no dysphagia, aspiration symptoms, or breathing difficulty.

Physical examination revealed a right-sided anterior cervical mass which crossed midline. The mass was soft and non-tender to palpation, there was no discoloration or sinus/fistula opening of the overlying skin, and there was no significant medical history of trauma, fever or congenital anomaly. Laboratory results were of no diagnostic importance and there was no sign of infection.

Chest radiograph showed right neck swelling with widening of the right paratracheal stripe and left tracheal deviation (Fig. 1A). Neck ultrasonography images obtained in an outside clinic revealed a huge cystic mass lying superficial to thyroid lobes. Contrast-enhanced computed tomography (CT) images demonstrated a well-defined, cystic and solid mass in upper mediastinum extending to the anterior neck (Fig. 1B). The mass ranged from the aortic arch to the thyroid cartilage level (C5–T4 level) and its longest diameter was 13 cm in the craniocaudal direction. The solid component in upper mediastinum exhibited heterogeneous enhancement and fat component (-85 Hounsfield units) (Fig. 1B, C) and connected with a multi-septated cystic component in the anterior neck without fluid-fluid level (Fig. 1B). The mass in the mediastinum abutted great vessels without vascular compromise, and no lymphadenopathy was noted. The cystic component compressed the right thyroid lobe without evidence of invasion (Fig. 1D). Trachea was deviated to the left side but without airway narrowing.

The patient was planned for complete resection. He underwent resection of the tumor via neck crease incision and median sternotomy under general anesthesia. The tumor was observed in the anterior neck. Adhesion between the capsule of the anterior neck mass and surrounding tissues was severe, and the capsule was ruptured during dissection. The yellowish fluid came out of the ruptured capsule and was removed. There was no apparent invasion into major blood vessels or adherent structures. The intrathoracic mass was then removed.

Grossly the mass had a pinkish yellow color, weighed 52.4 g and was of dimension 6.7 × 5.2 × 2.2 cm. The cyst was filled with the yellowish fluid and hemorrhage. Pathologic examination revealed a mature cystic teratoma in thymus (Fig. 1E) with acute and chronic inflammation. Its mature tissue components included epidermis, sebaceous glands and ducts, connective tissue, smooth and skeletal muscle, hair follicles, and adipose tissue (Fig. 1F). No immature components were observed.

The patient remained asymptomatic over 5 years of followup, and follow-up imaging studies showed no evidence of any residual or recurrent mass.

Benign cervical cysts are common during childhood and adolescence, and usually presents as progressively enlarging masses in the neck or as symptoms related to compression of surrounding tissues, such as, dysphagia, dyspnea, or recurrent episodes of infection (7). The differential diagnosis of cystic neck mass in an adult includes branchial cleft cyst, thyroglossal duct cyst, lymphatic malformation, neurenteric cyst, esophageal duplication cyst, and mature cystic teratoma. Cystic lesions of the neck are usually benign, but occult thyroid carcinoma presenting as a cervical cyst has occasionally been reported (8).

Mediastinal teratomas are usually asymptomatic and are often discovered incidentally by chest radiograph. Teratomas are generally slow-growing benign tumors and asymptomatic gradual enlargement is not uncommon. However, our patient showed a relatively rapid increase in the growth of the cystic component over a few months. The mechanism underlying the rapid growth of mature teratoma is unknown, though it has been reported that rapid enlargement is often associated with secondary infection or inflammation (9). In our case, the presence of yellowish fluid in the tumor and acute and chronic inflammation on pathology suggest that the cystic component of the tumor may have rapidly grown in size due to inflammation or infection and may have escaped into the neck. In addition, the patient had received needle aspiration for the cystic neck mass before admission, and bleeding after aspiration may have increased the size of the cyst. Fluid in cystic teratoma originates from secretions by intestinal epithelium, pancreatic tissue, structural degeneration (autolysis), and hemorrhage after needle aspiration (10).

In our patient, a mediastinal CT scan demonstrated the extent of the mass, but it can also detect fat, calcification or cystic components of mediastinal tumors and enable assessments of degrees of adjacent tissue invasion. Patients with a neck mass usually undergo ultrasonography, and ultrasonography well demonstrates relationships between masses and surrounding structures, especially with the thyroid gland and great vessels, although evaluation of mediastinum is difficult. Therefore, if intrathoracic extension of the neck mass is suspected on ultrasonography, neck CT with sufficient coverage of mediastinum should be performed to evaluate the mediastinal extension.

In conclusion, a cystic neck mass may rarely be caused by extension of mediastinal teratoma. Therefore, imaging studies including mediastinum are needed to investigate the cause of cystic neck mass and to confirm mass extent before treatment.