Mediastinal germ cell tumor
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2]
Synonyms and keywords: M-GCTs; Malignant germ cell tumors of the mediastinum;
Overview
Mediastinal germ cell tumor is a extragonadal tumor derived from germ cell remnants in the mediastinum and a cause of anterior mediastinal mass.[1][2] Malignant germ cell tumors of the mediastinum are uncommon, representing only 3 to 10% of tumors originating in the mediastinum. The most common cause of mediastinal germ cell tumor is teratoma. Other causes of mediastinal germ cell tumor, include: embryonal cell carcinoma, choriocarcinoma, yolk sac tumor, mixed germ cell tumor. Mediastinal germ cell tumor is more commonly observed among male patients between 15 to 30 years old. The most common risk factor in the development of mediastinal germ cell tumor is Klinefelter syndrome (47XXY). The majority of patients with mediastinal germ cell tumor are usually symptomatic at the time of diagnosis. Early clinical features include chest pain, dyspnea, and cough.
Historical Perspective
- Mediastinal germ cell tumor was first discovered by [scientist name], a [nationality + occupation], in [year] during/following [event].
- In [year], [gene] mutations were first identified in the pathogenesis of mediastinal germ cell tumor.
- In [year], the first [discovery] was developed by [scientist] to treat/diagnose mediastinal germ cell tumor.
Classification
- Mediastinal germ cell tumor may be classified according to histopathological subtype in 2 groups:
- Seminoma
- Non-seminomatous germ cell tumours (NSGCT)
- Embryonal cell carcinoma
- Choriocarcinoma
- Yolk sac tumour
- Teratoma (most common)
- Mixed germ cell tumor
Pathophysiology
- The pathogenesis of mediastinal germ cell tumor is characterized by the abnormal migration of germ cells during embryogenesis.
- Mediastinal germ cell tumor arises from germ cells, which are normally involved in the formation of o the gametes.
- Genetic mutations associated with the development of mediastinal germ cell tumor, include:[3]
- Sex chromosomal abnormalities
- Loss of 1p, 4q, and 6q
- Gain of 1q, 3, and 20q
- CCND2 gene
- p14ARF gene
- On gross pathology, findings of mediastinal germ cell tumor may include:
- Unencapsulated
- Homogenous fleshy mass with indistinct boundaries
- Invasion of adjacent structures
- On microscopic histopathological analysis findings of mediastinal germ cell tumor, include:
- Large tumor cells with clear cytoplasm
- Prominent nucleoli
Causes
- The most common cause of mediastinal germ cell tumor is teratoma.
- Other causes of mediastinal germ cell tumor, include:
- Embryonal cell carcinoma
- Choriocarcinoma
- Yolk sac tumour
- Mixed germ cell tumour
Differentiating Mediastinal Germ Cell Tumor from Other Diseases
- Mediastinal germ cell tumor must be differentiated from other diseases that cause chest pain, [clinical feature 2], and [clinical feature 3], such as:
- Lymphomas
- Soft tissue sarcoma
- Thymoma
- Neurogenic tumors
Epidemiology and Demographics
- Mediastinal germ cell tumor are uncommon
- Mediastinal germ cell tumor represent only 3 to 10% of tumors originating in the mediastinum
Age
- Mediastinal germ cell tumor is more commonly observed among young adults.
- Mediastinal germ cell tumor is more commonly observed among patients between 15 to 30 years old.
Gender
- Mediastinal germ cell tumor affects men and women equally.
- Males are more commonly affected with mediastinal germ cell tumor than females.
Race
- There is no racial predilection for mediastinal germ cell tumor.
Risk Factors
- The most common risk factor in the development of mediastinal germ cell tumor is Klinefelter syndrome (47XXY).
Natural History, Complications and Prognosis
- The majority of patients with mediastinal germ cell tumor are usually symptomatic at the time of diagnosis
- Early clinical features include chest pain, dyspnea, and cough.
- If left untreated, the majority of patients with mediastinal germ cell tumor may progress to develop metastasis, malignant pleural effusion, and respiratory failure.
- The most common complication of mediastinal germ cell tumor is superior vena cava syndrome.
- Prognosis is generally poor, and the median survival rate of patients with mediastinal germ cell tumor is approximately 5 months.
Diagnosis
Diagnostic Criteria
- The diagnosis of mediastinal germ cell tumor is made with the following diagnostic criteria:
- Hormone production (e.g. beta-HCG, AFP)
- No evidence of a primary tumor in the testes or ovaries
- Anterior mediastinal mass
- Obtuse angles with the lung
Symptoms
- Mediastinal germ cell tumors are usually asymptomatic and found incidentally.
- Symptoms of mediastinal germ cell tumor may include the following:
- Chest pain
- Dyspnea
- Cough
- Weight loss
- Fever
- Nausea
Physical Examination
- Patients with mediastinal germ cell tumor usually are well-appearing.
- Physical examination may be remarkable for:
- Dull percussion
- Tactile fremitus
- Reduced chest expansion
- Crackling or bubbling noises
- Present whispered pectoriloquy
Laboratory Findings
- Laboratory findings consistent with the diagnosis of mediastinal germ cell tumor, include:
- Elevation in serum alpha-fetoprotein (AFP)
- Elevation in beta-human chorionic gonadotropin (beta-hCG)
Imaging Findings
- Chest radiography is the initial imaging modality of choice for mediastinal germ cell tumor.
- On chest radiography, findings of mediastinal germ cell tumor, include:
- Displaced anterior junction line
- Obliterated cardiophrenic angles
- Obtuse angles with the mediastinum
- Obliterated retrosternal clear space
- Effacement/ dense ascending aorta
- On chest radiography, signs of mediastinal germ cell tumor, include:
- Hilum Overlay Sign: hilar vessels through the mass (the mass does not arise from the hilum)
- On CT, findings of mediastinal germ cell tumor, include:
- Anterior mediastinal mass
- Obtuse angles with the mediastinum
- Enhancing septations
Other Diagnostic Studies
- Mediastinal germ cell tumor may also be diagnosed using positron emission tomography.
- Findings on positron emission tomography, include:
- Useful to rule out the involvement of thyroid tissue.
Treatment
Medical Therapy
- Cisplatin-based chemotherapy is the treatment of choice for mediastinal germ cell tumors.
- Common therapies for mediastinal germ cell tumor, include:
- Etoposide
- Ifosfamide
- Cisplatin
- Bleomycin
- Alternative treatment for mediastinal germ cell tumor, include:
- Primary radiotherapy in the absence of metastatic disease
Surgery
- Surgery is the mainstay of therapy for mediastinal germ cell tumor.
- Radical resection in conjunction with chemotherapy/radiation is the most common approach to the treatment of mediastinal germ cell tumor.
Prevention
- There are no primary preventive measures available for mediastinal germ cell tumor.
- Once diagnosed and successfully treated, patients with mediastinal germ cell tumor are followed-up every year.
- Follow-up testing for mediastinal germ cell tumor, includes chest radiography and tumoral biomarkers.
References
- ↑ Alan Sandler (1997). "Mediastinal Germ Cell Tumors". Semin Respir Crit Care Med. 18 (4): 383-392. doi:10.1055/s-2007-1009353.
- ↑ "Mediastinal Germ Cell Tumor Imaging".
- ↑ Schneider DT, Schuster AE, Fritsch MK, Calaminus G, Göbel U, Harms D, Lauer S, Olson T, Perlman EJ (2002). "Genetic analysis of mediastinal nonseminomatous germ cell tumors in children and adolescents". Genes Chromosomes Cancer. 34 (1): 115–25. PMID 11921289.