Testicular cancer is a cancer that affects approximately one in 250 men, in the span of their lifetime with an incidence of about 0.4%. Notably, it affects most commonly men between 20 and 40, so of all cancers that affect men between the ages of 20 and 40, testicular cancer is the most common one. When we talk about how common it is, we talk about something called a bi-modal distribution. Which means that there's two spikes of peak incidents and one spike occurs between 20 and 40, another spike occurs around the age of 60. Men who get testicular cancer around the age of 60 tend to have a type of cancer called spermadicitic seminoma.
Testicular cancer as any other cancer is basically an abnormal or uncontrolled growth of cells within the testicle, and when some of those cells grow uncontrollably, and have the ability to both invade and spread to other parts of the body, we refer to that as testicular cancer. Of the various types of testicular cancer, cancers can arise from cells within the testicle where sperm is produced or there are other types of cells in an area called the interstitium, where they have certain cell types called leydig cells and sertoli cells.
Leydig cells are actually responsible for testosterone production. You can get tumors of the leydig cells, they're called leydig cell tumors. You can get tumors of the sertoli cells. Leydig and sertoli cell tumors are one type, but they actually represent the minority of testicular cancers, approximately 5.0% or less. Ninety-five percent of testicular cancers arise from the sperm producing cells, what we call the germ cell tumors. Of germ cell tumors, there are also many different types.
However, we broadly classify them into two broad categories, one type being seminoma and the second type being non-seminoma. Now non-seminoma can have multiple subtypes within that group and those include things like embryonal cell carcinoma, teratoma, choriocarcinoma and yolk-sac tumor. These are all types of testicular cancer. There are other types of cancer that can affect the testicle as well. These may be things such as lymphoma, which can involve other parts of the body and actually grow within the testicle itself. There are some more rare types of very aggressive cancers that can affect the testicle such as rabdomiosarcoma, sarcomas and these are very aggressive forms of cancer. They don't necessarily originate within the testicle.
However, there are also some benign conditions that affect the testicle that can often be confused for testicular cancer and there are tumors that arise in the tissue around the testicles that can be benign as well. But in general, when we refer to testicular cancer we're talking about cancers that arise from the testicles. The most common types we talk about, as I mentioned before, 95% are what we call germ-cell tumors with seminoma and non-seminoma. The reason we categorize, we put cancers into these separate, broad categories, seminoma versus non-seminoma, it really affects the way we manage the cancer, we treat the cancer. There are different algorithms and different pathways we use when evaluating, diagnosing and treating patients with these different types of cancers.