Pathogenesis and localization patterns
The term originates from the Greek word teratos, which translates to "monster". These unique neoplasms originate from pluripotent or totipotent stem cells. The core pathogenesis involves a disruption in embryogenesis: when undifferentiated germ cells are supposed to migrate to the area where the future gonads will form, their pathway is disrupted.
Depending on their anatomical location, two main groups are distinguished:
- Gonadal: affect the gonads directly (ovaries and testes).
- Extragonadal: the most important distinguishing feature of such lesions is that they are located strictly along the body midline. Typical locations include the sacrococcygeal region, retroperitoneum, mediastinum, as well as the pharynx and skull base.
Age-related epidemiology
The patient's age directly determines the most likely tumor location. This correlation follows distinct statistical patterns:
- Neonatal period and children under two years of age: sacrococcygeal teratomas are absolute predominant in this age group.
- Adolescence (from 15–16 years old): the incidence of ovarian teratomas sharply increases within the overall disease structure.
- Adulthood (from 20 to 49 years old): this period accounts for the peak incidence of the vast majority of testicular teratomas.
Morphological classification: mature and immature forms
The histological structure of teratomas is extremely diverse, as they can include derivatives of all three germ layers. Elements of ectodermal origin most commonly predominate.
Mature teratomas are characterized by the presence of well-differentiated tissues. Microscopic examination reveals formed epidermis and its appendages (glands, hair), areas of adipose and muscular tissue, and cartilage islands. Nervous system elements, such as mature glial tissue and clusters of ganglion cells, are frequently found.
Immature teratomas have a fundamentally different biological potential. The main diagnostic marker of immaturity is the presence of immature neural tissue within the structure. Pathologists distinguish three grades of immaturity (grades 1 to 3), graded according to the volume occupied by this immature component. A direct correlation is observed: the higher the grade of immaturity, the higher the likelihood of malignant biological potential of the neoplasm.
Sacrococcygeal teratoma
This is the most common type of tumor in infants and young children. Girls are affected by this pathology three times more often than boys.
The clinical presentation may be accompanied by severe complications as early as the intrauterine development stage. The presence of a tumor is often combined with polyhydramnios and the development of non-immune hydrops fetalis. Furthermore, the large size of the mass can create significant difficulties during delivery. Morphologically, sacrococcygeal neoplasms consist predominantly of mature tissues, often demonstrating pronounced organoid differentiation.
Teratocarcinomas and secondary malignant transformation
Malignant forms of teratomas (teratocarcinomas) belong to mixed germ cell tumors. Their cells differentiate into both embryonic and extraembryonic structures. Histologically, they represent a combination of teratoma elements with components of other aggressive tumors, such as large cell carcinoma, endodermal sinus tumor, or trophoblastic tumor.
The phenomenon of secondary malignant transformation is considered separately. Rarely, malignant transformation with the development of carcinoma can occur from derivatives of only a single germ layer within the teratoma. For example, squamous cell carcinoma can develop from stratified squamous epithelium, or carcinoma from thyroid elements. Such scenarios are described in the literature and are more common in adult patients.
Briefly: answers to topical questions
What macroscopic forms of ovarian teratomas are distinguished in pathological anatomy?
Pathological anatomy distinguishes solid, solid-cystic, and cystic macroscopic forms of ovarian teratomas.
- Immature teratoma is typically a unilateral solid (less commonly solid-cystic) tumor presenting as a soft, nodular, grayish-pink or whitish mass with foci of necrosis and hemorrhage.
- Mature teratoma (dermoid cyst) is a cystic form appearing as a sac with a dense fibrous capsule. On cross-section, it contains thick masses (sebum, hair in the form of tangles or strands), and well-formed teeth are frequently present.
What serum tumor markers are used to diagnose malignant teratomas?
To diagnose malignant teratomas and detect their malignant component, the levels of three main tumor markers are assessed in blood serum.
- Alpha-fetoprotein (AFP) is elevated in teratocarcinomas and in approximately one-third of immature teratomas cases.
- Human chorionic gonadotropin (hCG) – the free beta-subunit is evaluated.
- Lactate dehydrogenase (LDH) – the enzyme activity is assessed.
An initial elevation of AFP and/or hCG indicates a malignant process. The combined presence of elevated AFP and high hCG (greater than 1000 mIU/mL) indicates a malignant non-seminomatous germ cell tumor, even if a mature teratoma is morphologically identified.
What histological types of cancer can arise from secondary malignant transformation of a teratoma?
Secondary malignant transformation of a teratoma involves the development of cancer from derivatives of a single germ layer.
- Squamous cell carcinoma is the most common histological variant, developing from stratified squamous epithelium.
- Carcinoma arising from thyroid elements is another possible variant of malignant transformation.
Secondary malignant transformation of teratomas (including dermoid cysts) occurs extremely rarely. Such clinical situations are described in the literature and are significantly more common in adult patients than in children.
To memorize extragonadal locations, visualize a vertical axis (strictly along the body midline): pharynx → skull base → mediastinum → retroperitoneal space → sacrococcygeal region.
Class and exam questions
From which cells does a teratoma arise?
It develops from totipotent or pluripotent germ cells due to impaired normal migration during the formation of the embryonic gonads.
What determines the grade of immaturity of a teratoma?
The grade of immaturity (from grade 1 to 3) depends on the volume of immature neural tissue within the tumor structure. The greater its amount, the higher the risk of malignant behavior.
What is secondary malignant transformation of a teratoma?
This is a rare phenomenon, more frequently seen in adults, where a malignant tumor (carcinoma) develops from derivatives of only a single germ layer comprising the teratoma.
What else to study on this topic
- Characteristics of central nervous system and hematopoietic tissue involvement in pediatric malignant tumors.
- Differences between lymphangiomas with locally destructive growth and non-progressive lymphangiectasias.
- Juvenile nasopharyngeal angiofibroma: risks of profuse bleeding during surgical treatment.
- Classification criteria for fibromatoses in children (time of onset, histology, location).
- Infantile desmoid-type fibromatosis and its infiltrative growth pattern.
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