Although often described as benign, a teratoma does have malignant potential. In a UK study of 351 infants and children diagnosed with "benign" teratoma reported 227 with MT, 124 with IT. Five years after surgery, event-free survival was 92.2% and 85.9%, respectively, and overall survival was 99% and 95.1%. A similar study in Italy reported on 183 infants and children diagnosed with teratoma. At 10 years after surgery, event free and overall survival were 90.4% and 98%, respectively.

Depending on which tissue(s) it contains, a teratoma may secrete a variety of chemicals with systemic effects. Some teratomas secrete the "pregnancy hormone" human chorionic gonadotropin (βhCG), which can be used in clinical practice to monitor the successful treatment or relapse in patients with a known HCG-secreting teratoma. This hormone is not recommended as a diagnostic marker, because most teratomas do not secrete it. Some teratomas secrete thyroxine, in some cases to such a degree that it can lead to clinical hyperthyroidism in the patient. Of special concern is the secretion of alpha-fetoprotein (AFP); under some circumstances AFP can be used as a diagnostic marker specific for the presence of yolk sac cells within the teratoma. These cells can develop into a frankly malignant tumor known as yolk sac tumor or endodermal sinus tumor.

Adequate follow-up requires close observation, involving repeated physical examination, scanning (ultrasound, MRI, or CT), and measurement of AFP and/or βhCG.

Extraspinal ependymoma, usually considered to be a glioma (a type of non-germ cell tumor), may be an unusual form of mature teratoma.

The histology of EST is variable, but usually includes malignant endodermal cells. These cells secrete alpha-fetoprotein (AFP), which can be detected in tumor tissue, serum, cerebrospinal fluid, urine and, in the rare case of fetal EST, in amniotic fluid. When there is incongruence between biopsy and AFP test results for EST, the result indicating presence of EST dictates treatment. This is because EST often occurs as small "malignant foci" within a larger tumor, usually teratoma, and biopsy is a sampling method; biopsy of the tumor may reveal only teratoma, whereas elevated AFP reveals that EST is also present. GATA-4, a transcription factor, also may be useful in the diagnosis of EST.

Diagnosis of EST in pregnant women and in infants is complicated by the extremely high levels of AFP in those two groups. Tumor surveillance by monitoring AFP requires accurate correction for gestational age in pregnant women, and age in infants. In pregnant women, this can be achieved simply by testing maternal serum AFP rather than tumor marker AFP. In infants, the tumor marker test is used, but must be interpreted using a reference table or graph of normal AFP in infants.

EST can have a multitude of morphologic patterns including: reticular, endodermal sinus-like, microcystic, papillary, solid, glandular, alveolar, polyvesicular vitelline, enteric and hepatoid.

Schiller-Duval bodies on histology are pathognomonic and seen in the context of the endodermal sinus-like pattern.

The standard work-up for AT/RT includes:

- Magnetic resonance imaging (MRI) of the brain and spine

- Lumbar puncture to look for M1 disease

- Computed tomography (CT) of chest and abdomen to check for a tumor

- Bone marrow aspiration to check for bone tumors. Sometimes the physician will perform a stem cell transplant

- Bone marrow biopsy

- Bone scan

The initial diagnosis of a tumor is made with a radiographic study (MRI or CT-). If CT was performed first, an MRI is usually performed as the images are often more detailed and may reveal previously undetected metastatic tumors in other locations of the brain. In addition, an MRI of the spine is usually performed. The AT/RT tumor often spreads to the spine. AT/RT is difficult to diagnose only from radiographic study; usually, a pathologist must perform a cytological or genetic analysis.

Examination of the cerebrospinal fluid is important (CSF), as one-third of patients will have intracranial dissemination with involvement of the CSF. Large tumor cells, eccentricity of the nuclei, and prominent nucleoli are consistent findings. Usually only a minority of AT/RT biopsies have rhabdoid cells, making diagnosis more difficult. Increasingly it is recommended that a genetic analysis be performed on the brain tumor, especially to find if a deletion in the INI1/hSNF5 gene is involved (appears to account for over 80% of the cases). The correct diagnosis of the tumor is critical to any protocol. Studies have shown that 8% to over 50% of AT/RT tumors are diagnosed incorrectly.

Management of most fetal SCTs involves watchful waiting prior to any treatment. An often used decision tree is as follows:

- Perform detailed ultrasound exam including fetal echocardiogram and Doppler flow analysis

- If fetal high output failure, placentomegaly, or hydrops

- If fetus not mature, perform pregnancy termination or fetal intervention

- Else fetus mature, perform emergency Cesarean section

- Else no emergent problems, perform serial non-stress tests and ultrasound biophysical profiles and plan delivery, as follows

- If emergent problems develop, return to top of decision tree

- Else if SCT over 5–10 cm or polyhydramnios, perform early (37 weeks gestation) elective Cesarean section

- Else SCT small and no complications, permit term spontaneous vaginal delivery

Emergent problems include maternal mirror syndrome, polyhydramnios, and preterm labor. Poor management decisions, including interventions that are either premature or delayed, can have dire consequences. A very small retrospective study of 9 babies with SCTs greater than 10 cm diameter reported slightly higher survivorship in babies remaining in utero slightly longer.

In many cases, a fetus with a small SCT (under 5 or 10 cm) may be delivered vaginally. Prior to the advent of prenatal detection and hence scheduled C-section, 90% of babies diagnosed with SCT were born full term.

SCTs are very rare in adults, and as a rule these tumors are benign and have extremely low potential for malignancy. This estimation of potential is based on the idea that because the tumor existed for decades prior to diagnosis, without becoming malignant, it has little or no potential to ever become malignant. For this reason, and because coccygectomy in adults has greater risks than in babies, some surgeons prefer not to remove the coccyx of adult survivors of SCT. There are case reports of good outcomes.

Cytogenetics is the study of a tumor’s genetic make-up. Fluorescent "in situ" hybridization may be able to help locate a mutation or abnormality that may be allowing tumor growth. This technique has been shown to be useful in identifying some tumors and distinguishing two histologically similar tumors from each other (such as AT/RTs and PNETs). In particular, medulloblastmas/PNETs may possibly be differentiated cytogenetically from AT/RTs, as chromosomal deletions of 17p are relatively common with medulloblastoma and abnormalities of 22q11.2 are not seen. However, chromosomal 22 deletions are very comomon in AT/RTs.

In importance of the "hSNF5/INI1" gene located on chromosomal band 22q11.2 is highlighted, as the mutation’s presence is sufficient to change the diagnosis from a medulloblastoma or PNET to the more aggressive AT/RT classification. However, this mutation is not present in 100% of cases. Therefore, if the mutation is not present in an otherwise classic AT/RT immunohistochemical and morphologic pattern then the diagnosis remains an AT/RT.

The 1997 International Germ Cell Consensus Classification is a tool for estimating the risk of relapse after treatment of malignant germ cell tumor.

A small study of ovarian tumors in girls reports a correlation between cystic and benign tumors and, conversely, solid and malignant tumors. Because the cystic extent of a tumor can be estimated by ultrasound, MRI, or CT scan before surgery, this permits selection of the most appropriate surgical plan to minimize risk of spillage of a malignant tumor.

Access to appropriate treatment has a large effect on outcome. A 1993 study of outcomes in Scotland found that for 454 men with non-seminomatous (non-germinomatous) germ cell tumors diagnosed between 1975 and 1989, 5-year survival increased over time and with earlier diagnosis. Adjusting for these and other factors, survival was 60% higher for men treated in a cancer unit that treated the majority of these men, even though the unit treated more men with the worst prognosis.

Choriocarcinoma of the testicles has the worst prognosis of all germ cell cancers

MEM comprises a heterogeneous group of neoplasms believed to originate from the neural crest. First hints to this type of tumor were probably from Shuangshoti and Nestky (1971) and from Holimon and Rosenblum (1971) (2-3). Additional contributions were provided thereafter by Naka et al. (1975), Karcioglu et al. (1977), Cozzutto et al. (1982) and Kawamoto et al. (1987).

Kosem et al. collected 44 cases of MEM in a 2004 review and examined management data finding out that resection with pre- or post-surgery chemotherapy yielded the best results with one death only in 13. In the five cases reported by Mouton et al. an aggressive chemotherapy and adequate surgical excision granted a disease-free interval for 7 to 50 months. The attainability of radical surgical

ablation seems the most important prognostic factor (10).

The main features of this tumor is to comprise either ectodermal derivatives (neuroblasts and ganglion cells) or mesenchymal components mostly represented by plump, elongated cells in interlacing bundles often showing rhabdomyoblastic differentiation, including strap-like and racket-shaped cells (2-6). A myofibril-like structure and cross striations can be identified. Liposarcoma-like and chondroid foci can be an additional finding. Fibrosarcoma-like and fibrous histiocytoma-like areas can be observed as well as neurofibromatous and neuroblastic components with rosette formation. Ganglion cells can appear immature and atypical, they can be bi- or multinucleated and showing evidence of Nissl substance (2-6).

Rhabdomyoblasts and poorly differentiated small cells display positivity for desmin and myosin while neural areas are variably sensitive to S-100. Ganglion cells are strongly positive for NSE. It is important to point out that the ectodermal component may be sometimes scanty and can be overlooked whereas in specimens after chemotherapy the ganglioneuroma component is increased and even overwhelming.

Differential diagnosis should consider rhabdomyosarcoma, Triton tumor, teratoma, Wilms tumor and benign, mature ectomesenchymoma (ectomesenchymal hamartoma).

The 5-year disease-free survival for age >5 years is 50-60%. Another report found a similar 5-year survival at about 65% with 51% progression-free survival. The 10-year disease-free survival is 40-50%. Younger ages showed lower 5 and 10-year survival rates. A 2006 study that observed 133 patients found 31 (23.3%) had a recurrence of the disease within a five-year period.

GCNIS is not palpable, and not visible on macroscopic examination of testicular tissue. Microscopic examination of affected testicular tissue most commonly shows germ cells with enlarged hyperchromatic nuclei with prominent nucleoli and clear cytoplasm. These cells are typically arranged along the basement membrane of the tubule, and mitotic figures are frequently seen. The sertoli cells are pushed toward the lumen by the neoplastic germ cells, and spermatogenesis is almost always absent in the affected tubules. Pagetoid spread of GCNIS into the rete testis is common. Immunostaining with placental alkaline phosphatase (PLAP) highlights GCNIS cell membranes in 95 percent of cases. OCT3/4 is a sensitive and specific nuclear stain of GCNIS.

Imaging studies are performed before surgery or biopsy to preclude an intracranial connection. Images usually show a sharply circumscribed but expansile mass. It may be difficult to exclude the intracranial connection if the defect is small whether employing computed tomography or magnetic resonnance.

Use of telomerase inhibitors such as Imetelstat seem to have very low toxicity compared to other chemotherapy. The only known side effect of most telomerase inhibitors is dose-induced neutropenia. Neuropsychological deficits can result from resection, chemotherapy, and radiation, as well as endocrinopathies. Additionally, an increase in gastrointestinal complications has been observed in survivors of pediatric cancers.

The diagnostic process typically begins with a medical history workup followed by a medical examination by a physician. Imaging tests, such as CT scans and MRIs, help provide a clearer picture. The physician typically looks for fluid (or other bodily substance) filled sacs to appear in the scans, as is shown in the CT scan of a colloid cyst. A primary health care provider will refer an individual to a neurologist or neurosurgeon for further examination. Other diagnostic methods include radiological examinations and macroscopic examinations. After a diagnosis has been made, immunohistochemistry may be used to differentiate between epithelial cysts and arachnoid cysts. These examinations are useful to get a general idea of possible treatment options, but can be unsatisfactory to diagnose CNS cysts. Professionals still do not fully understand how cysts form; however, analyzing the walls of different cyst types, using electron microscopes and light microscopes, has proven to be the best diagnostic tool. This has led to more accurate cyst classification and correct course of action for treatments that are cyst specific. In the past, before imaging scans or tests were available, medical professionals could only diagnose cysts via exploratory surgery.

Women with benign germ cell tumors such as mature teratomas (dermoid cysts) are cured by ovarian cystectomy or oophorectomy. In general, all patients with malignant germ cell tumors will have the same staging surgery that is done for epithelial ovarian cancer. If the patient is in her reproductive years, an alternative is unilateral salpingoophorectomy, while the uterus, the ovary, and the fallopian tube on the opposite side can be left behind. This isn't an option when the cancer is in both ovaries. If the patient has finished having children, the surgery involves complete staging including salpingoophorectomy on both sides as well as hysterectomy.

Most patients with germ cell cancer will need to be treated with combination chemotherapy for at least 3 cycles. The chemotherapy regimen most commonly used in germ cell tumors is called PEB (or BEP), and consists of bleomycin, etoposide, a platinum-based antineoplastic (cisplatin).

Polyembryoma is a rare, very aggressive form of germ cell tumor usually found in the ovaries. Polyembryoma has features of both yolk sac tumour and undifferentiated teratoma/embryonal carcinoma, with a characteristic finding of embryoid bodies lying in a loose mesenchymal stroma.

It has been found in association with Klinefelter syndrome.

The most common missed lesion is within the nasal cavity, where a fibrosed nasal polyp may be considered. However, it does not have glial tissue. Further, a polyp usually has mucoserous glands. The lesion is frequently misintrepreted as scar in the subcutaneous tissues, but scar in a <2 year old child would be uncommon. Special stains are frequently required to highlight the diagnosis.

It is classified into two types, based on location in the body: peripheral PNET and CNS PNET.

An immature teratoma is a rare type of malignant (cancerous) germ cell tumor (type of tumor that begins in the cells that give rise to sperm or eggs).

Like a mature teratoma, it contains several different types of tissue such as hair, muscle, and bone. Unlike a mature teratoma, it contains primitive neuroepithelium.

Ependymomas make up about 5% of adult intracranial gliomas and up to 10% of childhood tumors of the central nervous system (CNS). Their occurrence seems to peak at age 5 years and then again at age 35. They develop from cells that line both the hollow cavities of the brain and the canal containing the spinal cord, but they usually arise from the floor of the fourth ventricle, situated in the lower back portion of the brain, where they may produce headache, nausea and vomiting by obstructing the flow of cerebrospinal fluid. This obstruction may also cause hydrocephalus. They may also arise in the spinal cord, conus medullaris and supratentorial locations. Other symptoms can include (but are not limited to): loss of appetite, difficulty sleeping, temporary inability to distinguish colors, uncontrollable twitching, seeing vertical or horizontal lines when in bright light, and temporary memory loss. It should be remembered that these symptoms also are prevalent in many other illnesses not associated with ependymoma.

About 10% of ependymomas are benign myxopapillary ependymoma (MPE). MPE is a localized and slow-growing low-grade tumor, which originates almost exclusively from the lumbosacral nervous tissue of young patients. On the other hand, it is the most common tumor of the lumbosacral canal comprising about 90% of all tumoral lesions in this region.

Although some ependymomas are of a more anaplastic and malignant type, most of them are not anaplastic. Well-differentiated ependymomas are usually treated with surgery. For other ependymomas, total surgical removal is the preferred treatment in addition to radiation therapy. The malignant (anaplastic) varieties of this tumor, malignant ependymoma and the ependymoblastoma, are treated similarly to medulloblastoma but the prognosis is much less favorable. Malignant ependymomas may be treated with a combination of radiation therapy and chemotherapy. Ependymoblastomas, which occur in infants and children younger than 5 years of age, may spread through the cerebrospinal fluid and usually require radiation therapy. The subependymoma, a variant of the ependymoma, is apt to arise in the fourth ventricle but may occur in the septum pellucidum and the cervical spinal cord. It usually affects people over 40 years of age and more often affects men than women.

Extraspinal ependymoma (EEP), also known as extradural ependymoma, may be an unusual form of teratoma or may be confused with a sacrococcygeal teratoma.

The ultrasound (US) features of struma ovarii are nonspecific, but a heterogeneous, predominantly solid mass may be seen. US demonstrates a complex appearance with multiple cystic and solid areas, findings that reflect the gross pathologic appearance of the tumor.

Magnetic resonance imaging findings may be more characteristic: The cystic spaces demonstrate both high and low signal intensity on T1- and T2-weighted images. Some of the cystic spaces may demonstrate low signal intensity on both T1- and T2-weighted images due to the thick, gelatinous colloid of the struma. No fat is evident in these lesions.

Second most common primary anterior mediastinal mass in adults. Most are seen in the anterior compartment and rest are seen in middle compartment. Hodgkin's usually present in 40-50's with nodular sclerosing type (7), and non-Hodgkin's in all age groups. Can also be primary mediastinal B-cell lymphoma with exceptionally good prognosis. Common symptoms include fever, weight loss, night sweats, and compressive symptoms such as pain, dyspnea, wheezing, Superior vena cava syndrome, pleural effusions (10,11). Diagnosis usually by CT showing lobulated mass. Confirmation done by tissue biopsy of accompanying nodes if any, mediastinoscopy, mediastinotomy, or thoracotomy. FNA biopsy is usually not adequate. (12,13,14) Treatment of mediastinal Hodgkin's involves chemotherapy and/or radiation. 5 year survival is now around 75%. (15) Large-cell type may have somewhat better prognosis. Surgery is generally not performed because of invasive nature of tumor.

Of all cancers involving the same class of blood cell, 2% of cases are mediastinal large B cell lymphomas.

Primitive neuroectodermal tumor (PNET) is a malignant (cancerous) neural crest tumor. It is a rare tumor, usually occurring in children and young adults under 25 years of age. The overall 5 year survival rate is about 53%.

It gets its name because the majority of the cells in the tumor are derived from neuroectoderm, but have not developed and differentiated in the way a normal neuron would, and so the cells appear "primitive".

PNET belongs to the Ewing family of tumors.