Teratomas are tumors that have embryologic origin arising from immature primordial cells of two or all three germ layers [2, 4]. The location can be gonadal or extragonadal. The hypothesis that has been accepted is that during early embryogenesis, a defect is occurring in the migration of multipotent germ cells along the urogenital ridge [4] (a theory suggested by Fine) [5]. In contrast, epidermoid and epidermoid cysts both arise from ectoderm and ectodermal inclusion cysts with the first lined by squamous epithelium and the latter composed of complex tissues [6].
The global incidence of teratoma is one in every 4000 births [2, 4]. There is no gender predilection in benign germ cell tumors. On the contrary, malignant types are more found in males compared to females [3]. Anterior mediastinal teratomas are reported to be the most common extragonadal teratoma by location [3,4,5]. About 1 to 3% of all germ cell tumors arise in the mediastinum [5]. It is estimated that germ cell tumors account for 15% and 24% of anterior mediastinal masses in adults and pediatric populations, respectively [3, 5].
The frequency of occurrence of teratomas is as follows: 40% in the sacrococcygeal region, 25% in the ovary, 18% in the neck and mediastinum, 12% in the testis, and 5% in the brain tissues [2].
The histologic classifications include mature and immature teratomas, teratoma with malignant features, seminoma, and non-seminomas [4, 5] as well as teratocarcinoma [5]. Mediastinal germ cell tumor is considered the most common histologic type ensued by seminoma [3]. Mature teratoma of the mediastinum is a slowly developing benign tumor [3, 4] that either arises from thymic parenchyma or developing near the thymus [3]. Due to the slow development of mature teratomas in the mediastinum [1], they are often discovered in routine chest radiographs [1, 3, 5]. In 60% of diagnosed cases, patients did not have any clinical complaints [2]. Commonly, young patients between 20 and 40 years present with symptoms [2, 4]. The clinical presentation of anterior mediastinal teratomas is produced because of the mass effects on adjacent organs [1,2,3,4] transformation to malignancy or spontaneous rupture [1]. Rupture of a mediastinal teratoma (36–41% of cases) is also observed which can cause severe symptoms such as chest pain, hemoptysis, dyspnea, coughing up hair, and sebaceous material [1]. Acute respiratory distress can result if a rupture has occurred into a tracheobronchial tree [1] leading to coughing up hair, and such presentation is considered pathognomonic for teratoma [4, 5]. Rupture of anterior mediastinal teratoma can also occur in pericardial and pleural spaces [3, 4] leading to pleural and pericardial effusions [3]. Conditions such as pneumothorax and acute cardiac tamponade are also reported [3]. One of the most common presentations of anterior mediastinal teratomas is superior vena cava obstruction [1].
The radiologic examination of choice is a chest CT scan in mediastinal teratomas [2,3,4,5] which can better evaluate the location, extension, and vascularity of such lesions [3, 4] compared to conventional radiography [2]. The typical CT features in mediastinal teratomas include well-demarcation with lobulated structure [4] regions of fat, cystic fluid contents, and areas of calcification [2, 4, 5]. The presence of the fat-fluid level is pathognomonic for teratomas [3, 4]. The characteristic findings of teratoma are the presence of well-differentiated tissues such as the teeth and hair [4]. Pancreatic enzymes are reported to have a role in the rupture of tumors [3]. If teratoma is ruptured, the findings can be fat globules at the site of rupture, air space opacities such as consolidation or atelectasis in the adjacent lung parenchyma, and pleura effusion [4]. If teratomas demonstrate thick-walled heterogeneous cystic mass with mural calcifications and internal fat components invading the pericardium and great vessels, then the possibility of malignancy is highly suspicious and needs to be ruled out [3]. Magnetic resonance imaging (MRI) is also a valuable tool to characterize the infiltration of mass. It will demonstrate signal intensities of fat, fluid, and calcification [3, 4]. Usually, CT-guided biopsy is performed for the determination of the benign or malignant nature of teratomas. Pericardial involvement is critical to a patient’s life and urgent intervention can be considered [4].
Usually, mature teratomas are benign with no malignant characteristics, but in few cases (1–3%), malignant transformation into sarcoma, adenocarcinoma, squamous cell carcinoma, and carcinoid tumor has been reported [2].
The treatment of choice is surgery by completely excising the tumor in non-malignant teratomas [2,3,4,5]. There is an excellent prognosis with a survival rate of almost 100% in mature teratomas. In immature teratomas, the lesions might depict aggressive behavior in adults and with poor prognosis [3]. Surgery is also helpful in establishing the diagnosis as well as maintaining long-term cure diminishing recurrence. The preferred method is the median sternotomy because it provides ease of access. Lateral thoracotomy can be useful in cases where an extension to hemithorax is noted [4]. Although mediastinal teratomas are not life-threatening by themselves; however, complications of extensive surgery that are carried out can be fatal, for instance, pneumonectomy which can lead to death [2]. The combination of surgery with chemotherapy can increase the survival rate in malignant teratomas [4].
