Teratoma
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A teratoma is a type of neoplasm (specifically, a tumor). The word teratoma comes from Greek and means roughly monstrous tumor. Definitive diagnosis of a teratoma is based on its histology: a teratoma is a tumor with tissue or organ components resembling normal derivatives of all three germ layers. Rarely, not all three germ layers are identifiable. The tissues of a teratoma, although normal in themselves, may be quite different from surrounding tissues, and may be highly inappropriate, even grotesque (hence the monstrous): teratomas (the plural infrequently teratomata) have been reported to contain hair, teeth, bone and very rarely more complex organs such as eyeball, torso, and hand. Usually, however, a teratoma will contain no organs but rather one or more tissues normally found in organs such as the brain, liver, and lung.
Teratomas belong to a class of tumors known as nonseminomatous germ cell tumor (NSGCT). All tumors of this class are the result of abnormal development of pluripotent cells: germ cells and embryonal cells. Teratomas of embryonal origin are congenital; teratomas of germ cell origin may or may not be congenital. The kind of pluripotent cell appears to be unimportant, apart from constraining the location of the resulting tumor in the body.
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[edit] Location and incidence
Teratomas derived from germ cells occur in the testes in males and ovaries in females. Teratomas derived from embryonal cells usually occur on the body midline: in the brain, elsewhere inside the skull, in the nose, in the tongue, under the tongue, and in the neck (cervical teratoma), mediastinum, retroperitoneum, and attached to the coccyx. However, teratomas may also occur elsewhere: very rarely in solid organs (most notably the heart and liver) and hollow organs (such as the stomach and bladder), and and more commonly on the skull sutures. Embryonal teratomas most commonly occur in the sacrococcygeal region: sacrococcygeal teratoma is the single most common tumor found in newborn babies.
Of teratomas on the skull sutures, approximately 50% are found in or adjacent to the orbit[1].
Incidence of teratomas by location:
Teratomas are rare, but not extremely rare. Sacrococcygeal teratomas are diagnosed at birth in 1 out of 40,000 babies. Given the current world population birth rate, this equals 5 per day or 1800 per year. Add to that number sacrococcygeal teratomas diagnosed later later in life, and teratomas in other locations, and the [incidence approaches 10,000 new diagnoses of teratoma per year.
[edit] Pathology classification of individual teratomas
Teratomas commonly are classified using a grading system: 0 or mature (benign); 1 or immature, probably benign; 2 or immature, possibly malignant (cancerous); and 3 or frankly malignant. See also cancer staging. Teratomas are also classified by their content: a solid teratoma contains only tissues (perhaps including more complex structures); a cystic teratoma contain only pockets of fluid or semi-fluid such as cerebrospinal fluid, sebum, or fat; a mixed teratoma contains both solid and cystic parts. Cystic teratomas usually are grade 0 and, conversely, grade 0 teratomas usually are cystic.
Grade 1 and 2 teratomas have the potential to become malignant (grade 3), and malignant teratomas have the potential to metastasize.
[edit] Initial diagnosis
Teratomas are thought to be present since birth, or even before birth, and therefore can be considered congenital tumors. However, many teratomas are not diagnosed until much later in childhood or in adulthood. Large tumors are more likely to be diagnosed early on. Sacrococcygeal and cervical teratomas are often detected by prenatal ultrasound. Additional diagnostic methods may include prenatal MRI. In rare circumstances, the tumor is so large that the fetus may be damaged or die. In the case of large sacrococcygeal teratomas, a significant portion of the fetus' blood flow is redirected toward the teratoma (a phenomenon called steal syndrome), causing heart failure, or hydrops, of the fetus. In selected cases, a fetal operation may be indicated.
Beyond the newborn period, symptoms of a teratoma depend on its location and organ of origin. Ovarian teratomas often present with abdominal or pelvic pain, caused by torsion of the ovary or irritation of its ligaments. Testicular teratomas present as a palpable mass in the testis; mediastinal teratomas often cause compression of the lungs or the airways and may present with chest pain and/or respiratory symptoms.
Some teratomas contain yolk sac elements, which secrete alpha-fetoprotein (AFP). Detection of AFP may help to confirm the diagnosis and is often used as a marker for recurrence or treatment efficacy, but is rarely the method of initial diagnosis. (Maternal serum alpha-fetoprotein, or MSAFP, is a useful screening test for other fetal conditions, including Down syndrome, spina bifida and abdominal wall defects such as gastroschisis).
[edit] Time of presentation
Teratomas of germ cell origin usually are found (ie, present) in adult men and women, but they may also be found in children and infants. Teratomas of embryonal origin are most often found in babies at birth, in young children, and, since the advent of ultrasound imaging, in fetuses.
[edit] Complications
Teratomas are not dangerous for the fetus unless there is either a mass effect or a large amount of blood flow through the tumor (known as vascular steal). The mass effect frequently consists of obstruction of normal passage of fluids from surrounding organs. The vascular steal can place a strain on the growing heart of the fetus, even resulting in heart failure, and thus must be monitored by fetal echocardiography.
After surgery, there is a risk of regrowth in place, or in nearby organs[3]
[edit] Treatment
The treatment of choice is complete surgical removal (ie, complete resection)[4][5]. Teratomas normally are well encapsulated and non-invasive of surrounding tissues, hence they are relatively easy to resect from surrounding tissues. Exceptions include teratomas in the brain, and very large, complex teratomas that have pushed into and become interlaced with adjacent muscles and other structures. Teratomas that are in surgically inaccessible locations, or are very complex, or are likely to be malignant (due to late discovery and/or treatment) sometimes are treated first with chemotherapy. For malignant teratomas, surgery typically is followed by chemotherapy. Prevention of recurrence does not require en bloc resection of surrounding tissues.
[edit] Follow-up evaluations
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 a yolk sac tumor or endodermal sinus tumor.
[edit] Special cases
[edit] Struma ovarii
A struma ovarii (literally: goiter of the ovary) is a rare benign teratoma that contains thyroid tissue. Despite its name, it is not restricted to the ovary. To be classified as a struma ovarii, thyroid tissue must be the predominant histology. Malignant transformation of struma ovarii is rare, occurring in only 5% of cases.
thyroid Hypothyroidism (Iodine deficiency, Cretinism, Congenital hypothyroidism, Goitre) - Hyperthyroidism (Graves-Basedow disease, Toxic multinodular goitre, Teratoma with thyroid tissue or Struma ovarii) - Thyroiditis (De Quervain's thyroiditis, Hashimoto's thyroiditis)
pancreas Diabetes mellitus (type 1, type 2, coma, angiopathy, ketoacidosis, nephropathy, neuropathy, retinopathy) - Zollinger-Ellison syndrome
parathyroid Hypoparathyroidism (Pseudohypoparathyroidism) - Hyperparathyroidism (Primary hyperparathyroidism, Secondary hyperparathyroidism, Tertiary hyperparathyroidism)
pituitary hyperfunction (Acromegaly, Hyperprolactinaemia, Syndrome of inappropriate antidiuretic hormone) - Hypopituitarism (Sheehan's syndrome, Kallmann syndrome, Simmonds' disease, Growth hormone deficiency) - Diabetes insipidus - Hypothalamic-pituitary dysfunction
adrenal Cushing's syndrome (Nelson's syndrome, Pseudo-Cushing's syndrome) - Congenital adrenal hyperplasia (due to 21-hydroxylase deficiency) - Hyperaldosteronism (Conn syndrome, Bartter syndrome) - Adrenal insufficiency (Addison's disease) - Hypoaldosteronism
gonads Polycystic ovary syndrome - 5-alpha-reductase deficiency - Hypogonadism - Delayed puberty - Precocious puberty
other Autoimmune polyendocrine syndrome - Carcinoid syndrome - Laron syndrome - Psychogenic dwarfism - Androgen insensitivity syndrome - Progeria
[edit] Dermoid cyst
A dermoid cyst is a teratoma containing hair (sometimes very abundant) and other structures characteristic of normal skin. The term is most often applied to teratoma on the skull sutures and in the ovaries of females.
[edit] Fetus in fetu
A fetus in fetu (or fœtus in fœtu) is a rare teratoma containing entire organ systems, even major body parts such as torso or limbs. It has often been interpreted as a fetus growing within its twin, as follows.
- Very early in a monozygotic twin pregnancy, in which both fetuses share a common placenta, one fetus wraps around and envelops the other. The enveloped twin becomes a parasite, in that its survival depends on the survival of its host twin, by drawing on the host twin's blood supply. Invariably the parasitic twin is anencephalic (without a brain) and lacks some internal organs, and as such is unable to survive on its own. The parasitic twin sometimes grows large enough to kill its host twin, in which case both twins die. Sometimes, however, the host twin survives and is delivered.
As such, this interpretation assumes fetus in fetu is a special complication of twinning, one of several grouped under the term parasitic twin. This interpretation can be psychologically extremely disturbing for the person who receives a diagnosis of fetus in fetu, or even of an ordinary teratoma.
[edit] Basic research
In light of the ethical issues surrounding the source of human stem cells, teratomas are being looked at as an alternative source for research since they lack the potential to grow into functional human beings.
[edit] Appearances in popular culture
- In season 2, episode 7 of the USA television program Grey's Anatomy, a man believes he is pregnant; he turns out to have a teratoma.
- In the film My Big Fat Greek Wedding, Aunt Voula tells a story about "a lump on the back of [her] neck" that contained "teeth, and a spinal column", probably a teratoma.
- In the film Breakin' All The Rules, Nikki describes a teratoma to Quincy.
- In The Troublesome Offspring of Cardinal Guzman (1992) by Louis de Bernières, Guzman's demons are caused by a teratoma.
[edit] References
- ^ Emedicine article on orbital dermoid cyst
- ^ Immature gastric teratoma of the lesser curvature in a male infant, Utsch et al (2001) Journal of Pediatric Gastroenterology and Nutrition 32:204-206
- ^ A recurred case of a mature ovarian teratoma presenting as a rectal mass (in Korean, abstract in English)
- ^ Teratomas in infancy and childhood. A 54-year experience at the Children's Hospital Medical Center Tapper and Lack (1983) Ann Surg. 198(3): 398–410
- ^ Germ-cell tumors in childhood and adolescence. GPOH MAKEI and the MAHO study groups Göbel et al (2000) Ann Oncol. 11(3): 263-271
[edit] See also
- Sanju Bhagat, a 36 year old man, diagnosed with a very large fetus in fetu.
- Ovarian cancer
- Testicular cancer
- Fetal surgery
- Germ cell tumour
- Seminoma (this page needing major revision)
- Nonseminoma
- Endodermal sinus tumor (also known as Yolk sac tumor)
