Embryonal carcinomas are a type of nonseminoma cancer that is present in about 40% of testicular cancer tumors, but pure embryonal carcinomas occur only 3-4% of the time. When seen under a microscope, these tumors can look like tissues of very early embryos. This type of nonseminoma tends to grow rapidly and spread outside the testicle. Embryonal carcinoma can increase blood levels of AFP and HCG. Visit National Institute of Health for more information.