Testicular cancer is a type of cancer that starts in the testicles. Testicles or testis (singular form of testicles) are part of the male reproductive system. Furthermore, these organs are usually smaller than a golf ball in adult men and are present within the scrotum or a bag of skin which hangs beneath the base of the penis.

The testicles have two primary functions:

  • They form male androgens (hormones) such as testosterone.
  • They also make sperm which are the male cells that fertilize a female egg cell to start a pregnancy.

The testicles consist of several types of cells which can develop into one or more types of cancer.

Germ Cell Tumors

Most of the testis tumors develop in the germ cells. These are that cells that are responsible for the production of sperm.

The two main types of germ cell tumors (GCT) in men are:

  • Seminomas
  • Non-seminomas

Both types of tumor are equally common; hence, why many testicular cancers contain both seminoma and nonseminoma cells. Moreover, experts refer to this mixture as nonseminomas because they grow and spread like non-seminomas. (1)

Seminomas

On the other hand, seminomas tend to grow and metastasize slower than non-seminomas. These type of germ cell tumor further splits to two types:

  • Classical seminoma: These type of seminoma usually occurs in men between 25 and 45 ages. Furthermore, it constitutes to 95% of seminomas.
  • Spermatocytic seminoma: On the other hand, this is a rare type and occurs in older men. The average age of people that get spermatocyte seminoma is about 65.

Some seminomas tend to increase blood levels the protein human chorionic gonadotropin (HCG) which is observable through a simple blood test. (2)

Non-seminomas

These types of germ cell tumors typically occur in between their early 30s and late teens. They are subdivided into four categories which include:

It further splits to different groups namely:

  • Embryonal carcinoma: It constitutes about 40% of testicular cancers. They tend to overgrow and spread outside the testicle.
  • Yolk sac carcinoma: They are named as yolk sac because their cells look like the yolk sac of an early human embryo. It is also known as endodermal sinus tumor, orchid blastoma or infantile embryonal carcinoma. It is the most common form of testicular cancer in children. Yolk sac carcinomas respond very well to treatment (chemotherapy) even if they metastasize.
  • Choriocarcinoma: This is a rare and aggressive type of testicular cancer in adults. It is likely to spread rapidly to distant organs and tissue. It also increases blood levels of HCG (human chorionic gonadotropin).
  • Teratoma: This type of cancer, however, has three layers when viewed under the microscope. These layers are the endoderm (innermost layer), mesoderm (middle layer) and ectoderm (outer layer). Nevertheless, pure teratomas of the testicles are very rare. It has three broad types: Mature, immature teratomas and teratomas with somatic-type malignancy

Carcinoma in situ

Germ cell cancers may be benign as a non-invasive form of the disease called carcinoma in situ (CIS) or intratubular germ cell neoplasia. It is hard to find CIS because it does not cause symptoms and does not form lump until it becomes invasive.

Stromal Tumors

These are tumors that develop in the supportive and hormone-producing tissues. They constitute a tiny percentage of testicular cancers.

The two main types of stromal tumor are:

Leydig cell tumors: These develop from the Leydig cells in the testicles that typically make male sex hormones (androgens like testosterone). However, most of them are benign and do not spread beyond the testicles. (3)

Sertoli cell tumors: On the other hand, these tumors develop from normal Sertoli cells which support and nourish the sperm-making cells. These tumors are also usually benign just like in Leydig cell tumors.

Secondary Testicular Cancer

These are cancers that start in other organs and then spread to the testicles. They are not actual testicular cancer but are named and treated based on where they started.

  • Leukemia
  • Lymphoma
  • Prostate, skin, kidney or lung cancers
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