Teratomas are tumours that form from primary germ cells, which are the cause of male (sperm) or female (ovary) gametes. These tumors can be benign or malignant.

Teratomas can occur at any age, in the foetus, child or adult (according to the study on teratomas and their characteristics in foetal and paediatric imaging published by the Jeanne-de-Flandre Hospital and the Oscar-Lambret Centre in Lille in 2015). Teratomas are often large, complex tumours that are classified as germ cell tumours. Their tissues originate from the three embryonic layers (one, two or three) at the origin of the various organs and tissues of the organism: endoderm, ectoderm and mesoderm. Most teratomas develop in the testicles in men (testicular teratoma), in the ovaries in women (ovarian teratoma), or in the sacro-coccygeal region in children. The treatment is mainly surgical and consists of the removal of the tumour.

1. Definition of teratoma

Derived from the Greek word 'teras', the term 'teratoma' literally means 'monstrous tumour'. This frightening name refers to two distinctive features. Firstly, the majority of teratomas are very large, and secondly, these tumours can contain various types of tissue. It is not uncommon to see hair, teeth, cartilage or bone. Teratomas are formed from certain embryonic cells, the primitive germ cells, which are the origin of male and female gametes. The observation of teratomas has led to one of the major scientific discoveries of our time: stem cells. Teratomas are composed of one, two or three layers of the embryonic layers (endoderm, ectoderm and mesoderm), and can be benign (mature teratomas), malignant (immature teratomas) or monodermal (malignant or benign, a rare and specialised form).

Teratomas can occur at any age, in the foetus, infant, child or even adult. According to the dossier on germ cell tumours published by the Gustave-Roussy Cancer Centre in 2022, half of the teratomas discovered in children are benign. Several types can be distinguished, depending on their location in the body, but it should be noted that 2/3 of these tumours concern the ovaries and the testicles (according to the dossier on germ cell tumours published by the Institute of Paediatric Haematology and Oncology in 2022). The main forms of teratomas are (Jeanne-de-Flandre Hospital and Oscar-Lambret Centre in Lille):

Ovarian teratoma: this can be of two types. Mature teratomas or dermoid cysts are benign and mainly affect teenagers and young fertile women (2.6 cases per 100,000 girls per year, Jeanne-de-Flandre Hospital and Oscar Lambret Centre in Lille). Malignant teratomas are rather rare in women.
Testicular teratoma: rare in men, it represents 5 to 10% of testicular cancers (according to the dossier on germ cell tumours published by the InfoCancer information portal in 2020), often malignant in adults.
Sacro-coccygeal teratoma: located between the coccyx and the lumbar vertebrae, the most frequent germinal tumour in children, its malignancy rate is estimated at 17% (Jeanne-de-Flandre Hospital and Oscar-Lambret Centre in Lille).
Cerebral teratoma: in the epiphysis, it is rare.
Mediastinal teratoma: in the thorax, between the lungs, it is rare.

The causes of teratoma development are not well known, and their treatment is essentially surgical.

2. Teratoma symptoms

Teratomas can occur at any age and in various parts of the body. In addition, they can take several forms (malignant, benign or monodermal). Because of their great diversity, it is difficult to define precise symptomatology. Some of these tumours may develop silently, while others will cause discomfort and clinical signs. Sometimes there may be swelling in the affected area (swelling). This is sometimes the case in patients with testicular teratomas. But more generally, the patient may also have (Jeanne-de-Flandre Hospital and Oscar-Lambret Centre in Lille, Gustave-Roussy Centre):

abdominal pain, infertility, metrorrhagia (abnormal bleeding from the vagina), pain during sexual intercourse in the case of ovarian teratoma;
pain in the testicles (only in the case of cancerous teratoma), abnormally high levels of alpha-fetoprotein (AFP) in the case of testicular teratoma;
urinary disorders, constipation, in case of sacro-coccygeal teratoma;
headaches, vomiting, and visual disturbances, in case of brain teratoma;
breathing difficulties in the case of mediastinal teratoma.

Note that if left untreated, ovarian teratomas can cause complications such as adnexal torsion, infection or cyst rupture.

3. Causes of teratoma

In patients who develop a teratoma, there is an abnormal development of tissue. However, the causes of this phenomenon are still unknown. It is therefore impossible to prevent the formation of such a tumour. Today, teratomas can be diagnosed at any stage of life: foetus, newborn, child, adolescent or adult. Moreover, they affect both men and women. It should be noted that malignant germ cell tumours in children are mainly detected in infants under the age of two and in adolescents (Gustave-Roussy centre). Researchers still do not know how to explain this distribution, but for some, there could be a link with an anomaly of the sex chromosomes (Klinefelter syndrome type).

4. Teratoma: when to consult?

Each teratoma has its own characteristics. Some are asymptomatic and can only be diagnosed late, which probably explains their large size. In many patients, the tumour is discovered by chance, during a routine visit or during a surgical operation, such as a caesarean section. Some women are diagnosed during a gynaecological appointment. The tumour may be found during a simple pelvic ultrasound, performed as part of a contraceptive pill prescription, or ovarian monitoring. Some teratomas cause clinical signs that may worry patients and prompt them to seek medical attention: the presence of a mass in the abdomen or lower abdomen, swollen testicle, abdominal pain, breathing difficulties, urinary problems, headaches, vomiting, visual problems, etc. Any abnormal symptom should lead the patient to consult the doctor for a clinical examination.

5. Teratoma examinations and diagnosis

Many patients discover the presence of a teratoma by chance during a routine check-up (uroscan during a urological appointment, pelvic scan at the gynaecologist's) or during surgery (caesarean section). Others visit a doctor after noticing some unusual and/or uncomfortable clinical signs. During the consultation, the doctor carries out a clinical examination. In some cases, the doctor can feel the swelling or mass. In order to make a diagnosis, the doctor will refer the patient for imaging tests, such as a CT scan or MRI (Institute of Paediatric Haematology and Oncology, Jeanne de Flandre Hospital and Oscar Lambret Centre in Lille). If an ovarian teratoma is suspected, an abdominal or pelvic ultrasound scan (the appearance of the tumour depends on its volume, location and level of calcification), as well as a pelvic MRI scan may be performed. The doctor may also carry out a blood test to determine the presence of tumour markers, secreted by certain teratomas, such as gonadotropic chorionic hormone (beta-HCG), alpha-fetoprotein (AFP) or lactate dehydrogenase (LDH). Finally, the tissue of the teratoma is analysed. Once the diagnosis has been made, it is important to carry out an extension assessment in order to understand the stage of the disease. The doctor looks for possible metastases in the lungs, liver, bones or brain.

6. Treatment of teratoma

The treatment strategy is mainly surgical, especially when the teratoma is benign. Teratomas are not (or only minimally) susceptible to chemotherapy or radiotherapy. In the case of a small, localised malignant teratoma, treatment may also be limited to surgery. However, it should be noted that malignant teratomas are sensitive to chemotherapy. If they are too large and/or too extensive, this treatment strategy is combined with surgery (according to the Canadian Cancer Society's 2022 Ovarian Germ Cell Cancer Treatment File). Surgery removes the teratoma and does not cause any harm, including fertility. In the case of a mature ovarian teratoma, the surgeon favours the least invasive technique, namely laparoscopy (exploration of the abdomen). In the case of a more complex teratoma, he may also perform an oophorectomy (removal of the ovaries). Sometimes only part of the affected ovary is removed. If both ovaries are removed, the patient can still give birth via egg donation. Finally, it should be noted that malignant brain tumours are often treated with radiotherapy. Once treated, patients must be followed up for several years: clinical examinations, imaging examinations, and sometimes analysis of tumour markers. This follow-up ensures that there is no recurrence and no long-term consequences (hearing and kidney functions, fertility).

7. How can teratoma be prevented?

Today, the causes of teratoma formation remain unknown. It is therefore impossible to prevent the occurrence of these germ cell tumours. Nevertheless, it is important to make a diagnosis as early as possible. In the foetus, teratomas are often detected early, thanks to the systematic use of obstetric ultrasound. In addition, women should have regular gynaecological check-ups, which may reveal the presence of a teratoma.

Sources :

Hôpital Jeanne-de-Flandre et centre Oscar-Lambret de Lille, Centre de lutte contre le cancer Gustave-Roussy, Institut d'hématologie et d'oncologie pédiatrique, Portail d'information InfoCancer, Société canadienne du cancer