A germ cell tumor occurs due to dysregulated growth and differentiation of germ cells.
Symptoms associated with germ cell tumors vary substantially from individual to individual. The most commonly reported signs and symptoms include abdominal pain, shortness of breath, wheezing, irregularity in the shape of the abdomen, irregular testicular size, swelling or mass that may be felt or seen, incontinence, leg weakness in case the malignant mass is in the sacrum, constipation and sometimes elevated beta-human chorionic gonadotropin and alpha-fetoprotein (AFP). In some cases, diagnosis can be difficult to establish because of similar presentations of many other medical conditions.
Workup of germ cell tumors necessarily involves many tests. It includes blood tests such as a complete blood count (CBC), chemistry, liver function tests (LFTs), kidney function tests (creatinine and blood urea nitrogen), tumor cell markers and genetic studies. Imaging studies are critical. CT scan, MRI, ultrasound and bone scans can all be used to assess the tumor and potential metastasis. A testicular ultrasound is performed when a diagnosis of malignant germ cell cancer is established to rule out cancer in the gonads.
Subtypes of germ cell tumors have particular characteristic features that differentiate them. Seminomas rarely invade adjacent structures and tend to metastasize to the bone and the lymph nodes. Calcifications can be detected within the tumor but they are uncommon. On histopathological analysis, the tumor appears bulky, lobulated, homogeneous and tends to present as an anterior mediastinal mass. On the other hand, nonseminomatous mediastinal germ cell tumors can metastasize to adjacent organs, the lymph nodes and to distant sites. They generally appear as irregular masses in the anterior mediastinum. Characteristic findings include areas of low attenuation resulting from necrosis, presence of cysts and hemorrhage. In contrast, mature teratomas exhibit calcifications in around 25% of samples. Uncommonly, a bone or a tooth are detected. Other characteristic features include a well defined, anterior mediastinal mass with irregular walls of various thickness, cyst formation with heterogeneous composition and the presence of fluid, calcium, and fat attenuation.
Treatment varies depending on several factors such as the extent of the tumor, the age of the patient, medical history, future expectations and tolerance to certain treatment options. A number of treatment modalities are available. These include surgery, radiation, chemotherapy, hormonal replacement when required, bone marrow transplantation, antibiotics to treat existing infections or to prevent their occurrence, supportive care to manage the severe side effects of the treatment and follow-up care to rule out recurrence, assess response to the treatment and control late complications.
Malignant germ cell tumors follow a staging procedure similar to epithelial ovarian cancers. For women who still desire a child, the unilateral salpingo-oophorectomy is recommended. This operation preserves the uterus, fallopian tube and ovary on the non-diseased site. On the other hand, women who do not desire more pregnancies can undergo a bilateral salpingo-oophorectomy with hysterectomy. In general, it is not possible to conserve both ovaries in case the disease is bilateral.
The prognosis of germ cell tumors can be assessed with the International Germ Cell Consensus Classification . The classification tool enables the physician to predict the risk of relapse for patients diagnosed with germ cell tumors, subsequent to treatment. On the other hand, computerized tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US) aid in visualizing the tumor and can thus establish a risk for malignant transformation. This is especially helpful as links have been established between cystic and benign tumors, and malignant and solid tumors . These imaging studies can further allow the selection of the best surgical plan. It is worth mentioning that choriocarcinoma of the testicles is considered the germ cell tumor with the worst prognosis.
The prognosis of germ cell tumors is affected by access to treatment. Early diagnosis improves 5-year survival, according to a 1993 study involving 454 men diagnosed between 1975-1989 with nonseminomatous germ cell tumors. Furthermore, treatment in cancer units improves survival by up to 60%, even for patients diagnosed with malignancies with the worst prognosis.
The causative mechanisms responsible for germ cell tumors remain unknown. Nonetheless, some inherited and non-inherited defects have been shown to significantly increase the risk. For example, cryptorchidism, defined as the failure of the descent of the testes to the scrotum, results in an increased risk of testicular germ cell cancer. The age at which the testicle is surgically ascended (orchidopexy) plays a critical role. Patients who had the operation before 13 years have a relative risk of 2.23 of developing testicular germ cell cancer. In contrast, those who underwent orchidopexy at 13 years or later have a relative risk of 5.4 . It is important to note that the development of cancer with cryptorchidism does not always occur. On the other hand, an additional or a missing sex chromosome may lead to defects in the reproductive system, and subsequent development of germ cell tumors.
Scientists suggest that extragonadal germ cell tumors result from a defect during embryogenesis. This eventually leads to misplacement of primordial germ cells, and ultimately to local transformation and tumor growth. Extragonadal germ cell tumors tend to occur in the midline of the body. In particular, in the anterior abdominal wall, liver, stomach, prostate, vagina, the thyroid, the submandibular area, the suprasellar area, the palate and in the orbit.
On the other hand, risk factors for nonseminomatous testicular tumors are various. These include gonadal dysgenesis, exposure to chemical carcinogens, orchitis, trauma, prenatal exposure to high levels of estradiol and a history of testicular cancer. One study, conducted on 44,684 Swedish men and published in 2005 after 25 years of follow-up, reported a link between testicular cancer and elevated cholesterol levels . However, future studies need to expand on and confirm these findings in other populations.
Extragonadal germ cell tumors make up 5 to 10% of all germ cell tumors in the United States. In Norway, the incidence of extragonadal germ cell tumors has been reported to be 0.5 for every 100,000 individuals, representing 2% of testicular cancers . On the other hand, intracranial germ cell tumors are rare in the West and make up 0.3 to 3.4% of all intracranial tumors. However, they represent 2.1 to 12.7% of all cases of intracranial tumors in Japan . Studies by Rusner et al performed on 16,000 patients diagnosed with malignant extragonadal germ cell tumors between 1998 and 2008 concluded that different etiologies are associated with differences in age-specific and age-standardized incidence .
On the other hand, nonseminomatous testicular tumors have a peak incidence between 20 and 34 years of age. They tend to occur more frequently among whites than African Americans. They remain, however, relatively infrequent, despite the fact that they are the most commonly encountered solid malignancy among young and healthy individuals. The incidence of nonseminomatous testicular tumors in the United States is 5.44 for every 100,000 individuals . There have been some recent alarming signals. Studies report an increase in the incidence of 46% in the United States between 1975-2001, even after the introduction of platinum-based chemotherapy . Other reports suggest that incidence has substantially increased among military personnel between 1988 and 1996 .
Several genetic mutations are involved in malignant transformation. In particular, an increase in the 12p gene, due to a duplication of the chromosomal arm or of the gene itself, has been strongly linked to germ cell tumors. This mutation is present in both advanced disease and carcinoma in situ. Other important features include an overexpression of the CCND2 gene. CCND2 is normally present on the 12p13 band and results in the activation of cdk4/6. CDk4/6 helps move the cell from G1 to S in the cell cycle.
On the other hand, intracranial germ cell tumors are characterized by the imbalance of p53 and mdm2 levels. Normally, mdm2 inhibits p53, induces apoptosis and regulates the G1 to S checkpoint. Mdm2 is under the control of ARF, which in turn results from the expression of the p14ARF gene. ARF binds mdm2 and degrades it . In intracranial germ cell tumors, a mutation in ARF leads to an increase in mdm2 levels and a subsequent impairment of p53.
Nonseminomatous germ cell tumors can be classified into four subtypes: teratomas, choriocarcinomas, embryonal carcinomas and yolk sac tumors. Mixed tumors represent a mixture of all of these histological types. Some tumors possess both seminomatous and nonseminomatous components. They are generally considered nonseminomatous because the latter determines prognosis and response to treatment.
There are no current preventive measures for germ cell tumors.
Germ cells are the cells that constitute the reproductive organs in both males and females. Germ cell tumors can be either benign or malignant. They tend to occur in the reproductive organs and in the midline of the body and are classified into germinomas or seminomas and nonseminomatous germ cell tumors . The latter usually grow faster, are less responsive to chemotherapy and radiotherapy and have a poor prognosis.
Germ cell tumors are rare tumors. The incidence of nonseminomas is approximately 5.44 for every 100,000 individuals. The latter tend to affect healthy and young individuals between the ages of 20 and 34 years. The underlying causative mechanisms remain unknown, although several risk factors have been identified. For example, cryptorchidism, or the failure of the descent of the testes into the scrotum, increases the risk of testicular germ cell cancer. Other risk factors include genetic or inherited conditions that affect sex chromosomes and that can lead to abnormalities in the reproductive organs. The pathophysiologic mechanisms underlying germ cell tumors involve genetic mutations of critical cell regulatory agents. A mutation in the 12p gene due to a chromosomal arm duplication is strongly associated with germ cell tumors. Other molecules that play an important role are mdm2, cdk4/6, and p53.
Patients with germ cell tumors present with a range of symptoms depending on the site and location of the tumor. The most prominent symptoms are abdominal pain, shortness of breath, wheezing, irregular testicular size and the appearance of a mass along the midline of the body. Workup includes blood tests, imaging studies, and biopsy. Treatment varies according to the patient and the subtype of the tumor. It encompasses chemotherapy, radiotherapy, surgery, bone marrow transplantation and hormonal replacement. A typical chemotherapy regimen for germ cell tumors consists of bleomycin, etoposide, and cisplatin.
Germ cells are the cells that develop during the formation of the embryo and later become part of the reproductive organs. Abnormal tumors from these cells occur when there is dysregulated growth and differentiation. These tumors can occur in the reproductive organs or outside. This is because many germ cell tumors remain in other parts of the body during the development of the embryo. Germ cell tumors can be benign or malignant and are classified histologically into many types. One type called seminoma or germinoma has significantly better prognosis than nonseminomatous tumors.
Patients can present with a multitude of symptoms, making the diagnosis sometimes particularly challenging. The most common symptoms are abdominal pain, the presence of a mass in the body, irregular testicular size, shortness of breath and wheezing. The physician must perform a very broad workup to establish diagnosis and guide treatment. The workup will include blood tests, imaging with x-ray, computerized tomography or magnetic resonance imaging, biopsy and histological analysis.
Treatment of germ cell tumors can vary considerably based on the specific circumstances of the patient and the type of tumor involved. Chemotherapy, radiotherapy, surgery, bone marrow transplantation and hormonal replacement are all potential treatment modalities.