Polyembryoma is a type oftumor 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 distinctivelook because they are composed of many parts that are shaped like embryos, one of the earliest stages of a developing human during pregnancy. Symptoms of a polyembryoma may include an unusual bump or mass in the abdomen which can cause pain in some individuals; puberty at an unusually young age (known as precocious puberty); or irregularities in a female's menstruation. Treatment begins with surgery and may be followed by chemotherapy and/or radiation therapy. The cause of polyembryoma is not yet known.