Germ cell cancer is a type of growth that originates from germ cells, which are the fundamental reproductive cells in the body. These cells normally develop into sperm in males and eggs in females. Germ cell tumors can be benign (non-cancerous) or malignant, meaning they are cancerous and have the potential to spread to other areas of the body. This type of cancer is relatively rare, often affecting children, teenagers, and young adults.
Origin of Germ Cells and Their Role
Germ cells are distinctive cells that carry the genetic information necessary for reproduction. In males, these cells mature into sperm, while in females, they become eggs. Their primary function involves transmitting genetic material from one generation to the next.
During early embryonic development, these germ cells are formed and then migrate to the developing reproductive organs, the testes in males and ovaries in females. They possess the inherent ability to differentiate into various cell types found throughout the body. This multipotency means that a single germ cell can theoretically give rise to any type of tissue.
Where Germ Cell Cancers Appear
While germ cell cancers most frequently arise in the gonads, specifically the testes in males and ovaries in females, they can also develop in other parts of the body. These sites outside the reproductive organs are known as extragonadal locations. The occurrence of extragonadal germ cell tumors is thought to be a result of germ cells migrating and settling in unusual locations during embryonic development.
Common extragonadal sites include the mediastinum, which is the area between the lungs in the chest, the retroperitoneum, located at the back of the abdomen, and the sacrococcygeal region, near the tailbone. Less commonly, these tumors can also form in the brain, particularly in the pineal gland. In infants and children, sacrococcygeal tumors are more common, while in teens and young adults, the mediastinum is a more frequent extragonadal site.
Major Categories of Germ Cell Cancer
Germ cell tumors are broadly classified into two main categories: seminomas (or dysgerminomas in females) and non-seminomas. This classification is based on how the tumor cells appear under a microscope. Seminomas generally grow and spread more slowly than non-seminomas.
Non-seminomatous germ cell tumors tend to be more aggressive and grow more quickly. This group includes several distinct subtypes such as embryonal carcinoma, yolk sac tumor, choriocarcinoma, and teratoma. Embryonal carcinoma is characterized by primitive, embryonic-like cells. Yolk sac tumors, also known as endodermal sinus tumors, are most common in children and can produce alpha-fetoprotein (AFP).
Choriocarcinoma is a rare and aggressive type of non-seminoma that can secrete human chorionic gonadotropin (hCG). Teratomas are unique in that they can contain various mature or immature tissues, such as hair, teeth, muscle, or bone. Teratomas can be benign (mature teratomas) or malignant (immature teratomas). Mixed germ cell tumors, containing elements of both seminoma and non-seminoma types, are also common.
How Germ Cell Cancer is Identified
Diagnosis typically begins with a physical examination and a review of symptoms, which vary depending on the tumor’s location. For example, a lump or swelling in a testicle, or abdominal pain in cases of ovarian or abdominal tumors, might be present. Swelling or a mass in the tailbone area can indicate a sacrococcygeal teratoma, while chest pain, cough, or breathing problems may suggest a mediastinal tumor.
Blood tests are a significant diagnostic tool, often checking for specific tumor markers. Elevated levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH) can indicate the presence of certain germ cell tumors. Imaging studies, such as ultrasound, CT scans, and MRI, are used to visualize the tumor’s size and location. An ultrasound is often an initial step, followed by CT or MRI for more detailed imaging. A definitive diagnosis is typically made through a biopsy, where a tissue sample from the tumor is removed and examined under a microscope.