What causes teratoma?

Teratomas are congenital disorders primarily caused by abnormal embryonic differentiation during development. Such developmental abnormalities may result from exposure to ionizing radiation or adverse drug effects, leading to malignant transformation.

Teratomas consist of multiple tissue types derived from different germ layers. When a teratoma is detected in an embryo, termination of pregnancy is generally recommended; otherwise, the fetus may develop congenital abnormalities. Moreover, teratomas tend to progressively enlarge as the embryo develops. Most teratomas are malignant tumors, and their pathogenesis is mainly attributed to abnormal embryonic development induced by exposure to ionizing radiation or drug-related side effects, resulting in fetal malformation.

What Causes Teratomas?

Types

Teratomas arise from two or three germ layers and thus may contain any tissue type found in the human body. Their location closely corresponds to midline or paramidline regions of embryologic body cavities—such as the sacrococcygeal region, mediastinum, retroperitoneum (paraspinal), ovary, and testis. Based on histological maturity, teratomas are classified as benign, malignant, or mixed. Teratomas carry a risk of malignant transformation, which increases with age—especially in sacrococcygeal teratomas, which may undergo malignant change shortly after birth. However, some teratomas are malignant at initial presentation.

Classification

Malignant teratomas grow rapidly, often penetrating their capsule to invade surrounding tissues and metastasize via lymphatic or hematogenous routes to regional lymph nodes, lungs, and bone. In contrast, the vast majority of cystic teratomas are benign, whereas solid teratomas more frequently exhibit malignancy. Histopathological grading of teratomas aids in prognostication and therapeutic decision-making: Grade 0 or Grade I teratomas rarely undergo malignant transformation and seldom metastasize, whereas Grade III teratomas carry the highest risk of malignancy.

Etiology

During embryogenesis, certain pluripotent cells or tissues may escape normal regulatory control by organizers and inducers, detaching from the developing embryo and undergoing genetic mutations that disrupt normal differentiation—ultimately giving rise to teratomas. If such aberrant events occur later in embryonic development, residual pluripotent cells retain the capacity to differentiate into tissues representing all three germ layers (ectoderm, mesoderm, and endoderm), thereby forming mature teratomas. The Hensen’s node (also known as the primitive node) at the caudal end serves as a major site of pluripotent cell aggregation; hence, sacrococcygeal teratomas are the most common type. Familial clustering has been observed: among six families, 17 individuals were diagnosed with sacrococcygeal teratomas, affecting both males and females—suggesting a hereditary component in the pathogenesis of sacrococcygeal teratomas.

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