Epidemiology of Benign Cystic Teratoma
Teratomas are considered as the most common neoplasm in newborns, with an estimated incidence of 1 per 20,000 births. Teratomas can be either mature “benign” or immature “malignant.” Up to 20% of ovarian tumors are mature cystic teratomas.
Benign teratomas can arise from any germ-cell line in both males and females, but testicular germ-cell teratomas are rare and account for only 5% of testicular tumors. Mediastinal benign teratomas are found in 8% of the patients presenting with a mediastinal tumor.
The majority of teratomas occur in females, 80%, and there is a clear gender discrepancy, especially for sacrococcygeal teratomas.
While sacrococcygeal teratomas can be diagnosed in newborns, gonadal teratomas, such as ovarian cystic teratomas and testicular teratomas, are usually diagnosed in adolescents and adults.
Complications of Benign Cystic Teratoma
Teratomas occurring in the sacrococcygeal area carry a high morbidity and mortality risk due to antenatal and delivery-related complications. Patients with large teratomas diagnosed in utero can have an intra-teratoma hemorrhage incident, which, if severe enough, can cause nonhemolytic hydrops fetalis.
Benign ovarian teratomas can become infected or rupture. Additionally, larger teratomas can cause ovarian torsion. Testicular teratomas, even though rare, carry a high risk of metastasis even when they are mature.
Pathophysiology of Benign Cystic Teratoma
Teratomas are germ-cell tumors arising from one or all of the three germ-cell layers. These tumors arise from totipotent cells, which are capable of differentiating into a wide range of cell types and can form functional tissue.
Totipotent cells are abundant in the gonads at the early stages of development, which explains why teratomas are commonly diagnosed in this location. Totipotent cells can be considered as embryonic stem cells, and any type of tissue can form within the tumor such as hair, teeth, skin, muscle and endocrine, as seen in the figure.
The majority of these tumors are mature and well differentiated into cystic teratomas. Such mature teratomas are not expected to metastasize unless they occur in the testis.
Immature teratomas are usually diagnosed in post-pubertal boys, and are much more likely to metastasize and be malignant. Malignant transformation can happen in benign cystic teratomas, especially ovarian ones.
Clinical Presentation of Benign Cystic Teratoma
The clinical presentation of teratomas is highly dependent on their location. Sacrococcygeal teratomas are usually diagnosed antenatally by ultrasound. Polyhydramnios is a commonly associated finding with sacrococcygeal teratomas. If not diagnosed antenatally, they are usually diagnosed at the time of birth.
On the other hand, ovarian teratomas are usually not obvious and are diagnosed incidentally. In the majority of the cases, the patient undergoes an imaging study or an abdominal surgery for another indication, only to find an incidental teratoma in the ovary. In a few cases, ovarian teratomas can cause torsion or bleeding and such patients can present with abdominal pain, anemia or an abdominal mass on physical examination.
Testicular teratomas present as a diffuse enlargement of the testis that is painless. Discomfort can be a presenting symptom as well. When pain is present, testicular torsion should always be excluded.
Diagnostic Work-up for Benign Cystic Teratoma
Laboratory investigations are not helpful in confirming the diagnosis of a teratoma, but are beneficial in excluding associated complications such as malignancy transformation and anemia. Alpha-fetoprotein and beta-human chorionic gonadotropin are both reported to be higher in patients with malignant teratomas.
The most important diagnostic work-up for teratomas is imaging. In patients diagnosed antenatally, follow-up serial ultrasound studies are indicated to exclude associated complications, such as hydrops fetalis and polyhydramnios. Fetal magnetic resonance imaging (MRI) can be used to study the tumor’s characteristics and invasiveness.
Patients who present with an abdominal mass benefit from ultrasonography and computerized tomography (CT) scanning.
The ultrasonography demonstration of teratomas is the same regardless of their location and includes shadowing echoes of different densities, bright echoes and fluid-fluid levels.
Transvaginal ultrasound is the most sensitive and specific to diagnose and differentiate ovarian cystic teratomas from other ovarian tumors.
Abdominal CT scanning is indicated to evaluate the liver and lymph nodes for possible metastasis. Abdominal CT scanning can be also valuable in the characterization of the mature teratoma. Several dividing septa, fat and calcification can be appreciated on a CT scan of a teratoma.
Testicular teratomas should be evaluated by ultrasonography. The degree of maturity and invasiveness are important in making the decision of whether to spare the testis or not in the surgery.
While mediastinal teratomas are rare, they can cause more serious complications due to their proximity to vital organs such as the heart, lungs and major arteries. Chest CT and MRI are indicated to evaluate the tumor’s extension and involvement of other vital organs, while echocardiography can be used to assess the heart function in these patients.
If the imaging studies raise suspicion of malignancy, fine-needle aspiration or a core biopsy can be used to exclude possible malignant component. Histological examination of a benign cystic teratoma shows an inner lining of keratinized squamous epithelium, hair, bronchial and gastrointestinal cells, neuronal cells, retinal cells or teeth.
Treatment of Benign Cystic Teratoma
Sacrococcygeal teratomas can cause hydrops fetalis due to a rich vascular flow to the tumor. In these patients, fetoscopic laser ablation or vascular coiling, are indicated to limit blood flow to the tumor. Additionally, if the antenatal evaluation reveals a large teratoma, caesarean delivery is indicated to avoid delivery complications.
If the sacrococcygeal teratoma does not cause any major complications antenatally, then tumor excision can be delayed until birth. Complete teratoma excision, along with the coccyx, is indicated to avoid recurrence.
The distinction between benign and malignant ovarian teratomas is essential because, in benign cystic teratomas, it is possible to salvage the ovary. Up to 40% of the cases are bilateral, and salpingo-oophorectomy will result in ovarian failure and infertility in these women.
While the current standard is to perform an open abdominal surgery, a laparoscopy can be offered as an option to selected cases. While a laparoscopy reduces post-operative pain, blood loss and results in faster recovery, patients should understand that the risks of recurrence and of the tumor’s spillage are higher.
A Teratoma’s spillage can cause peritonitis or a foreign-body-reaction and abdominal adhesions. Testicular teratomas are usually excised along with the testis, unless they happen in a prepubertal boy and are clearly benign.
Mediastinal teratomas should be excised completely along with any adherent structures to the tumor such as the lung or pericardium. Total excision of mediastinal teratomas is curative.