Testicular cancer is the number one cancer in men between the ages of 15 and 35. There are about 5 cases per 100,000 males – which is a pretty big number, as far as tumors go. Let’s take a quick look at the clinical presentation, pathologic subtypes, and prognosis of this common cancer.

Clinical Presentation
Testicular cancer usually presents as a firm, painless enlargement of the testis. Sometimes, this takes the form of a focal lesion, perhaps the size of a grain of rice or a pea. Other times, the tumor presents as a generalized enlargement or a change in consistency in the testicle.

Types of testicular cancer
By far, the most common types of tumor in the testicle are germ cell tumors. There are occasional lymphomas, or sex cord-stromal tumors, but those are in the minority. It’s just the opposite in the ovary – germ cell tumors are very uncommon (the most common ovarian tumor is a surface epithelial tumor). Weird.

Germ cell tumors of the testis arise from primitive cells that can differentiate along gonadal lines (producing seminomas) or transform into a totipotential cell population (producing non-seminomas). Non-seminomas can remain largely undifferentiated (as in embryonal carcinoma) or they can differentiate along extraembryonic cell lines (as in yolk sac tumor or choriocarcinoma).

Seminoma accounts for about half of all testicular cancers. Arising from the germinal epithelium of the seminiferous tubule, seminoma cells are large, with distinct cell borders, pale nuclei, and a sparse associated lymphocytic infiltrate (as seen in the image above). In general, seminomas have a really good prognosis. Even when metastatic, they are exquisitely sensitive to radiation and chemotherapy.

The remainder of cases is comprised of non-seminomas (often, there is a mixture of a few types). Specific types of non-seminomas include embryonal tumor (composed of undifferentiated stem cells), yolk sac tumor (composed of yolk sac cells), choriocarcinoma (composed of immature placental cells) and teratoma (composed of mature or immature somatic tissue cells).  Although non-seminomas have a worse prognosis than seminomas, newer platinum-based chemotherapeutic agents have improved overall survival.

Tumor markers
There are a couple tumor markers in specific types of testicular cancer that you should know about. Human chorionic gonadotropin (hCG), a hormone normally made by placental cells, is increased in choriocarcinoma and sometimes in seminoma. Alpha-fetoprotein (AFP) is a protein normally made by several different cell types, including fetal yolk sac cells. It is increased in yolk sac tumors and embryonal carcinoma. These markers are great for staging and follow-up (if you know the patient’s baseline tumor maker level, you can follow it over time, and if it starts going up, it probably means the patient’s tumor is growing bigger).

Overall, the prognosis in testicular cancer is good. With early detection, the cure rate approaches 100%. Even if you detect it later on, though, testicular cancer (especially seminoma) is very sensitive to radiation and chemotherapy and usually carries a very good prognosis.