Teratogenous neoplasms - teratomas and teratocarcinomas. Anatomic sites, microscopic & gross pathomorphology
A teratoma is a tumor made of different types of tissue (e.g. bone, hair, dermal, cartilaginous, neural), commonly forming in ovaries, testicles or tailbone. A teratoma is a type of germ cell tumor, and can be classified as mature (generally benign) and immature (may be malignant), we can determine the nature of the teratoma based on histology.
Mature teratomas
- Mature tissues derived from all three germ cell layers (ectoderm, endoderm and mesoderm)
- Usually contain cysts lined by epidermis with dermal appendages (e.g. hair follicles), so known as dermoid cysts
- Commonly found in ovaries, mostly unilateral up to about 10 cm in diameter. About 1% become malignant, generally however, asymptomatic.
Mature cystic teratoma (dermoid cyst) of the ovary, opened: hair and sebaceous material from the skin-lined cyst wall.
Image: “Mature Cystic Teratoma of the Ovary (5560431170)” by Ed Uthman from Houston, TX, USA, CC BY 2.0, via Wikimedia Commons.
Immature Teratomas
- Found early in life, average age 18. They are bulky and predominantly solid (unlike mature teratomas which are cystic).
- Microscopic examination shows immature tissues, minimally differentiated.
- Often ovarian or testicular, solid on examination
- Generally malignant and can form metastases
Remember: in the ovary a mature teratoma is benign, but in an adult man every testicular teratoma, even a fully mature one, is treated as malignant (in prepubertal boys they are usually benign). In immature teratomas the grade, and so the risk, rises with the amount of immature neuroepithelium.