what is Testicular Cancer?

Testicular cancer is a disease in which cancer develops in one or both of the testicles. It occurs when germ cells experience abnormal growth. Germ cells are highly specialized cells that form gametes (cells that make sperm), and like stem cells, have the potential to form any cell in the body. Normally these cells lie dormant until sperm fertilizes an egg. If germ cells become cancerous, they multiply, forming a mass of cells called tumors that begin to invade normal tissue. When this happens, these cells could potentially form a variety of embryonic like features including, but not limited to, hair, nails, teeth etc.

Testicular cancer can metastasize, meaning that it can spread to other parts of the body through blood and lymph vessels, forming new tumors. Testicular cancer spreads most often to the abdomen, liver, lungs, bones and brain. Testicular cancer can spread rapidly and is deadly if left untreated.

Testicular cancer has a very fast onset. If not detected early, the cancerous tumors can grow rapidly with the ability to double in size in just 10 - 30 days.

Testicular cancer is on the rise and can affect any male from infancy to the elderly. An estimated 9,720 will be diagnosed in 2025 according to the American Cancer Society. The highest rate of diagnoses are males between the ages of 15 - 44. It is estimated that 1 out of 250 males will be diagnosed with testicular cancer at some point in their lifetime. Largely due to the lack of awareness & early detection it is estimated 600 deaths will occur in 2025. That's 600 too many. Statistics can be found on cancer.org.

Different Types of Testicular Cancer

Germ Cell Tumors (GCTs)

95% of malignant tumors arising in the testes begin in the cells that produce sperm, known as germ cells. Germ cell tumors make up over 90% of testicular cancer diagnoses. There are two main types of germ cell tumors: seminoma and non-seminoma. They each occur about half of the time. When diagnosed with testicular cancer, both seminoma and non-seminoma cells are usually present - in this case they are treated as non-seminoma, because they grow and spread like non-seminomas.

1. Seminoma Germ Cell Tumors

   Arise from sperm producing germ cells of the testicles and grow or spread at a slower rate than non-seminomas. Seminomas are most likely to occur in men aged 30 to 50. Seminomas are slow-growing tumors that respond well to surgery, chemotherapy and radiation.

   There are two sub-types of seminoma tumors:

   • Classical seminoma - 95% of all seminomas are classical

   • Spermatocytic seminoma - this is a rarer type of seminoma that occurs in older men (average age 65)

2. Non-seminoma Germ Cell Tumors

   Non-seminomas (NSGCT) are more rare, more aggressive and tend to grow more quickly than seminoma tumors. These can include a combination of different cell types (known as “mixed NSGCT”) and tend to react differently according to the cell type. Non-seminoma tumors usually develop earlier in life, usually in men in their late teens to early 30’s. These non-seminoma tumor types include:

• Embryonal carcinomas are a type of non-seminoma 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 non-seminoma tends to grow rapidly and spread outside the testicle. Embryonal carcinoma can increase blood levels of tumor marker proteins called alpha-fetoprotein (AFP)* and human chorionic gonadotropin (HCG)* but does not always.

• Yolk sac carcinomas (also known as yolk sac tumor, endodermal sinus tumor, infantile embryonal carcinoma or orchidoblastoma) are so named because their cells look like the yolk sac of an early human embryo.

  Yolk sac carcinoma is the most common form of testicular cancer in children. When they do occur in children, these tumors are usually treated successfully. When yolk sac tumors develop in adults, however, they are of more concern, especially if they are "pure". Yolk sac carcinomas respond very well to chemotherapy, even if they have spread. This type of tumor almost always increases blood levels of AFP*.

• Choriocarcinoma is a very rare and aggressive type of testicular cancer that occurs mostly in adults.

  Pure choriocarcinoma tends to spread rapidly to other organs of the body, including the lungs, bone and brain. More often, choriocarcinoma cells are present with other types of non-seminoma germ cells, creating a mixed germ cell tumor. This type of tumor increases blood levels of HCG*.

• Teratomas are germ cell tumors that when seen under the microscope, look like each of the three cell layers of a developing embryo: endoderm (internal cells such as the gastrointestinal tract & lungs), the mesoderm (bones and muscle cells) and the ectoderm (skin and nerve cells). Teratomas display a diverse variety of biological behaviors, are aggressive in nature and are best diagnosed and treated quickly. These cancers account for about 3-7% of NSGCTs and 50% of mixed GCTs (1).

  There are three types of Teratoma Tumors:

  • Mature teratomas are tumors formed by cells similar to cells of adult tissues. They are generally benign and rarely spread to nearby tissues or other parts of the body. These tumors are highly curable with surgery, but some will recur or come back.

    Immature teratomas are less well-developed cancers with cells that look like those of an early embryo. Unlike mature teratomas, this type is more likely to metastasize outside of the testicle and is also more likely to recur years after treatment. 

    Teratoma with malignant transformation is a very rare cancer. This cancer has some areas that look like mature teratomas as well as areas where the cells have become a different type of cancer that develops outside of the testicle in tissues such as muscles, the lungs, the intestines, or the brain. 

• Primitive neuroectodermal (PNET) tumor is a highly malignant component of testicular germ cell tumors. Patients with PNET do not respond to cisplatin-based chemotherapy but could benefit from a CAV (cyclophosphamide, doxorubicin, and vincristine regimen alternating with ifosfamide plus etoposide (IE) after an RPLND surgery.

These tumor types are determined after removal of the testicle. Non-seminoma tumors have a slightly less favorable prognosis than seminomas but are still very treatable by chemotherapy and radiation.

Stromal Tumors

Testicular tumors that arise in the supportive and hormone-producing areas (the stroma) of the testicles. Such tumors are known as gonadal stromal tumors. They account for about 5% of adult testicle tumors and 20% of childhood testicle tumors. The two main types are Leydig and Sertoli cell tumors.

• Leydig cell tumors develop from normal Leydig cells of the testicle, which are the cells that normally produce androgens (male sex hormones). Leydig cell tumors can develop in both children and adults. They often produce androgens but sometimes produce estrogens. Most Leydig tumors are benign (non-cancerous). Although most Leydig cell tumors do not spread beyond the testicle and are cured by surgical removal, a small number metastasize. Metastatic Leydig cell tumors have a poor prognosis as they do not respond well to chemotherapy and radiation.

• Sertoli cells act as supportive stromal cells of the testicles that nourish sperm producing cells. Sertoli cell tumors are also usually benign but once they spread throughout the body can be unresponsive to chemo and radiation therapy. 

Carcinoma In Situ (CIS or Intratubular Germ Cell Neoplasia)

Abnormal cells that have not spread outside the walls of the seminiferous tubules. Seminiferous tubules house the germ cells that produce sperm inside of the testicle. This cancer can be difficult to find and diagnose because it generally does not cause symptoms or form a lump. The best treatment for CIS remains a topic of ongoing debate; since it does not always progress to invasive cancer, treatment decisions are generally made on a case-by-case basis.

Secondary Testicular Cancers

Cancers that have metastasized to the testicles from other organs and are treated based on where they started. While they are not true testicular cancers, they still have a profound impact on those affected. Lymphoma in men over 50, leukemia in boys as well as cancers of the prostate, lung, skin (melanoma) and other organs can all spread to the testicles.

*A Common Misconception: Pregnancy Tests and Testicular Cancer

There is a common misconception that a pregnancy test can be used to detect testicular cancer. While some testicular tumors produce a hormone called Human Chorionic Gonadotropin (HCG) which is associated with pregnancy—it is important to note that not all testicular cancers produce HCG. As such, pregnancy tests are not a reliable diagnostic tool for detecting testicular cancer.

If you suspect any symptoms or have concerns, it is essential to seek medical advice for a proper diagnosis. Early detection and professional evaluation are crucial.

Source citations:

Farci F, Shamsudeen S. Testicular Teratoma. [Updated 2023 Apr 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK567728/

Types of testicular cancer. Johns Hopkins Medicine. (2024, August 21). https://www.hopkinsmedicine.org/health/conditions-and-diseases/testicular-cancer/types-of-testicular-cancer