A cancerous (malignant) tumour that starts in germ cells (sperm cells).

Non-seminoma is a type of testicular cancer (cancer that starts in the testicle). It is classified based on the type of normal cells the cancer cells look like under a microscope. Embryonal carcinoma looks like the tissue of an early embryo. Choriocarcinoma looks like normal tissue of the placenta. Yolk sac tumour looks like normal tissue of the yolk sac of an early embryo. Teratoma can look like many types of tissue, including hair, muscle and bone.