Embryonal teratomas most commonly occur in the sacrococcygeal region: sacrococcygeal teratoma is the single most common tumor found in newly born humans.

Of teratomas on the skull sutures, approximately 50% are found in or adjacent to the orbit. Limbal dermoid is a choristoma, not a teratoma.

Teratoma qualifies as a rare disease, but is not extremely rare. Sacrococcygeal teratoma alone is diagnosed at birth in one out of 40,000 humans. Given the current human population and birth-rate, this equals five per day or 1800 per year. Add to that number sacrococcygeal teratomas diagnosed later in life, and teratomas in other locales, and the incidence approaches ten thousand new diagnoses of teratoma per year.

A teratoma is a tumor made up of several different types of tissue, such as hair, muscle, or bone. They typically form in the ovaries, testicles, or tailbone and less commonly in other areas. Symptoms may be minimal if the tumor is small. A testicular teratoma may present as a painless lump. Complications may include ovarian torsion, testicular torsion, or hydrops fetalis.

They are a type of germ cell tumor (a tumor that begins in the cells that give rise to sperm or eggs). They are divided into two types mature and immature. Mature teratomas include dermoid cysts and are generally benign. Immature teratomas may be cancerous. Most ovarian teratomas are mature. In adults, testicular teratomas are generally cancerous. Definitive diagnosis is based on a tissue biopsy.

Treatment of tailbone, testicular, and ovarian teratomas is generally by surgery. Testicular and immature ovarian teratomas are also frequently treated with chemotherapy.

Teratomas occur in the tailbone in about 1 in 30,000 newborns making them the most common tumor in this age group. Females are affected more often than males. Ovarian teratomas represent about a quarter of ovarian tumors and are typically noticed during middle age. Testicular teratomas represent almost half of testicular cancers. They can occur in both children and adults. The term comes from the Greek words for "monster" and "tumor".

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.

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.

Maternal complications of pregnancy may include mirror syndrome. Maternal complications of delivery may include a Cesarean section or, alternatively, a vaginal delivery with mechanical dystocia.

Complications of the mass effect of a teratoma in general are addressed on the teratoma page. Complications of the mass effect of a large SCT may include hip dysplasia, bowel obstruction, urinary obstruction, hydronephrosis and hydrops fetalis. Even a small SCT can produce complications of mass effect, if it is presacral (Altman Type IV). In the fetus, severe hydronephrosis may contribute to inadequate lung development. Also in the fetus and newborn, the anus may be imperforate.

Later complications of the mass effect and/or surgery may include neurogenic bladder, other forms of urinary incontinence, fecal incontinence, and other chronic problems resulting from accidental damage to or sacrifice of nerves and muscles within the pelvis. Removal of the coccyx may include additional complications. In one review of 25 patients, however, the most frequent complication was an unsatisfactory appearance of the surgical scar.

Gonadoblastoma is most often associated with an abnormal chromosomal karyotype, gonadal dysgenesis, or the presence of a Y chromosome in over 90% of cases. Gonadoblastoma has been found in association with androgen insensitivity syndrome, mixed gonadal dysgenesis and Turner syndrome, especially in the presence of Y chromosome-bearing cells.

A gonadoblastoma is a complex neoplasm composed of a mixture of gonadal elements, such as large primordial germ cells, immature Sertoli cells or granulosa cells of the sex cord, and gonadal stromal cells. Most gonadoblastomas are benign.

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.

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

A dysgerminoma is a type of germ cell tumor; it usually is malignant and usually occurs in the ovary.

A tumor of the identical histology but not occurring in the ovary may be described by an alternate name: seminoma in the testis or germinoma in the central nervous system or other parts of the body.

Dysgerminoma accounts for less than 1% of ovarian tumors overall. Dysgerminoma usually occurs in adolescence and early adult life; about 5% occur in pre-pubertal children. Dysgerminoma is extremely rare after age 50. Dysgerminoma occurs in both ovaries in 10% of patients and, in a further 10%, there is microscopic tumor in the other ovary.

Abnormal gonads (due to gonadal dysgenesis and androgen insensitivity syndrome) have a high risk of developing a dysgerminoma. Most dysgerminomas are associated with elevated serum lactic dehydrogenase (LDH), which is sometimes used as a tumor marker.

Some investigators suggest that this distribution arises as a consequence of abnormal migration of germ cells during embryogenesis. Others hypothesize a widespread distribution of germ cells to multiple sites during normal embryogenesis, with these cells conveying genetic information or providing regulatory functions at somatic sites.

Extragonadal germ cell tumors were thought initially to be isolated metastases from an undetected primary tumor in a gonad, but it is now known that many germ cell tumors are congenital and originate outside the gonads. The most notable of these is sacrococcygeal teratoma, the single most common tumor diagnosed in babies at birth.

Of all anterior mediastinal tumors, 15–20% are germ cell tumors of which approximately 50% are benign teratomas.

Granulosa cell tumours (or granulosa-theca cell tumours or folliculoma) are tumours that arise from granulosa cells. These tumours are part of the sex cord-gonadal stromal tumour or non-epithelial group of tumours. Although granulosa cells normally occur only in the ovary, granulosa cell tumours occur in both ovaries and testicles (see Ovarian cancer and Testicular cancer). These tumours should be considered malignant and treated in the same way as other malignant tumours of ovary. The ovarian disease has two forms, juvenile and adult, both characterized by indolent growth, and therefore has high recovery rates.

The staging system for these tumours is the same as for epithelial tumours and most present as stage I. The peak age at which they occur is 50–55 years, but they may occur at any age.

Juvenile granulosa cell tumour is a similar but distinct rare tumour. It too occurs in both the ovary and testis. In the testis it is extremely rare, and has not been reported to be malignant. Although this tumour usually occurs in children (hence its name), it has been reported in adults.

A struma ovarii (literally: goitre of the ovary) is a rare form of monodermal teratoma that contains mostly thyroid tissue, which may cause hyperthyroidism.

Despite its name, struma ovarii is not restricted to the ovary.

The vast majority of struma ovarii are benign tumors; however, malignant tumors of this type is found in a small percentage of cases.

10-year survival rates for mucinous tumors is excellent in the absence of invasion.

In the case of borderline tumors confined to the ovary and malignant tumors without invasion, the survival rates are 90% or greater. In invasive mucinous cystadenocarcinomas, the survival is approximately 30%

Ovarian cystadenoma is a cystic benign tumor of the ovary. Two types are recognized: serous and mucinous.

Dysgerminomas, like other seminomatous germ cell tumors, are very sensitive to both chemotherapy and radiotherapy. For this reason, with treatment patients' chances of long-term survival, even cure, is excellent.

A dermoid cyst is a teratoma of a cystic nature that contains an array of developmentally mature, solid tissues. It frequently consists of skin, hair follicles, and sweat glands, while other commonly found components include clumps of long hair, pockets of sebum, blood, fat, bone, nails, teeth, eyes, cartilage, and thyroid tissue.

As dermoid cysts grow slowly and contain mature tissue, this type of cystic teratoma is nearly always benign. In those rare cases wherein the dermoid cyst is malignant, a squamous cell carcinoma usually develops in adults, while infants and children usually present with an endodermal sinus tumor.

Industrialized nations, with the exception of Japan, have high rates of epithelial ovarian cancer, which may be due to diet in those countries. Caucasian are at a 30–40% higher risk for ovarian cancer when compared to Black and Hispanic people, likely due to socioeconomic factors; white women tend to have fewer children and different rates of gynecologic surgeries that affect risk for ovarian cancer.

Cohort studies have found a correlation between dairy consumption and ovarian cancer, but case-control studies do not show this correlation. There is mixed evidence regarding the effect of red meat and processed meat in ovarian cancer.

Tentative evidence suggests that talc, pesticides, and herbicides increase the risk of ovarian cancer. The American Cancer Society notes that as of now, no study has been able to accurately link any single chemical in the environment, or in the human diet, directly to mutations that cause ovarian cancer.

Estrogens are produced by "functioning" tumours, and the clinical presentation depends on the patient's age and sex.

- Female

- If the patient is postmenopausal, she usually presents with abnormal uterine bleeding, and in some cases hemoperitoneum.

- If the patient is of reproductive age, she would present with menometrorrhagia. However, in some cases she may stop ovulating altogether.

- If the patient has not undergone puberty, early onset of puberty may be seen.

- these tumors tend to have late recurrencies ( even after 30 years )

Alcohol consumption does not appear to be related to ovarian cancer. Other factors that have been investigated, such as smoking, low levels of vitamin D in the blood, presence of inclusion ovarian cysts, and infection with human papilloma virus (the cause of some cases of cervical cancer), have been disproven as risk factors for ovarian cancer. The carcinogenicity of perineal talc is controversial, because it can act as an irritant if it travels through the reproductive tract to the ovaries. Case-control studies have shown that use of perineal talc does increase the risk of ovarian cancer, but using talc more often does not create a greater risk. Use of talc elsewhere on the body is unrelated to ovarian cancer. Sitting regularly for prolonged periods is associated with higher mortality from epithelial ovarian cancer. The risk is not negated by regular exercise, though it is lowered.

Increased age (up to the 70s) is a risk factor for epithelial ovarian cancer because more mutations in cells can accumulate and eventually cause cancer. Those over 80 are at slightly lower risk.

Smoking tobacco is associated with a higher risk of mucinous ovarian cancer; after smoking cessation, the risk eventually returns to normal.A diet high in animal fats may be associated with ovarian cancer, but the connection is unclear. Diet seems to play a very small role, if any, in ovarian cancer risk.

Higher levels of C-reactive protein are associated with a higher risk of developing ovarian cancer.

Fibromas (or fibroid tumors or fibroids) are benign tumors that are composed of fibrous or connective tissue. They can grow in all organs, arising from mesenchyme tissue. The term "fibroblastic" or "fibromatous" is used to describe tumors of the fibrous connective tissue. When the term "fibroma" is used without modifier, it is usually considered benign, with the term fibrosarcoma reserved for malignant tumors.

Fertility subsequent to treatment of surface epithelial-stromal tumors depends mainly on histology and initial

staging to separate it into early borderline (or more benign) versus advanced stages of borderline (or more malignant). Conservative management (without bilateral oophorectomy) of early stage borderline tumors have been estimated to result in chance of over 50% of spontaneous pregnancy with a low risk of lethal recurrence of the tumor (0.5%). On the other hand, in cases of conservative treatment in advanced stage borderline tumors, spontaneous pregnancy rates have been estimated to be 35% and the risk of lethal recurrence 2%.

These lesions usually present in neonates, although they may not come to clinical attention until adulthood (for cosmetic reasons). There is no gender predilection. They are present in approximately 3-6 per 1000 live births.

Most treatments involve some combination of surgery and chemotherapy. Treatment with cisplatin, etoposide, and bleomycin has been described.

Before modern chemotherapy, this type of neoplasm was highly lethal, but the prognosis has significantly improved since.

When endodermal sinus tumors are treated promptly with surgery and chemotherapy, fatal outcomes are exceedingly rare.

Transitional cell carcinoma of the ovary, abbreviated TCC of the ovary, is a rare type of ovarian cancer that has an appearance similar to urothelial carcinoma (also known as transitional cell carcinoma).