teratoma (testicular)

Last reviewed 01/2018

Teratomas are a type of gonadal tumour occurring both in the ovaries and the testes. Derived from multipotent cells, they contain tissue from all three germ layers and exhibit a wide range of differentiation.


  • 5% are differentiated teratoma - TD - composed entirely of mature tissue
  • 55% are malignant teratoma intermediate - MTI - contains both differentiated mature tissue and malignant areas
  • 36% are malignant teratoma undifferentiated - MTU - no differentiated tissue present; all components malignant
  • 4% are malignant teratoma trophoblastic - MTT - contains cytotrophoblast and syncytiotrophoblast; often occurs as a sub-variant of one of the others

Note that about 40% of teratomas occur mixed with seminomas.

The vast majority secrete human chorionic gonadotropin and/or alpha-feto protein which can be measured in the serum and used as a tumour marker. They are less radiosensitive than seminomas.