Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Polyembryoma ?
    ### Response:
    Polyembryoma is a type of tumor that develops from the cells of the gonads (testes in men or ovaries in women).  Such tumors are called germ cell tumors.  Polyembryomas have a distinctive look because they are composed of many parts that are shaped like embryos, one of the earliest stages of a developing human during pregnancy.
    