Trophoblastic neoplasms derive from trophoblastic tissue. Examples include:

- Choriocarcinoma

- Hydatidiform mole

Gestational trophoblastic disease (GTD) is a term used for a group of pregnancy-related tumours. These tumours are rare, and they appear when cells in the womb start to proliferate uncontrollably. The cells that form gestational trophoblastic tumours are called trophoblasts and come from tissue that grows to form the placenta during pregnancy.

There are several different types of GTD. Hydatidiform moles are benign in most cases, but sometimes may develop into invasive moles, or, in rare cases, into choriocarcinoma, which is likely to spread quickly, but which is very sensitive to chemotherapy, and has a very good prognosis. Gestational trophoblasts are of particular interest to cell biologists because, like cancer, these cells invade tissue (the uterus), but unlike cancer, they sometimes "know" when to stop.

GTD can simulate pregnancy, because the uterus may contain fetal tissue, albeit abnormal. This tissue may grow at the same rate as a normal pregnancy, and produces chorionic gonadotropin, a hormone which is measured to monitor fetal well-being.

While GTD overwhelmingly affects women of child-bearing age, it may rarely occur in postmenopausal women.

Gestational trophoblastic disease (GTD) may also be called gestational trophoblastic tumour (GTT).

Hydatidiform mole (one type of GTD) may also be called molar pregnancy.

Persistent disease; persistent GTD: If there is any evidence of persistence of GTD, usually defined as persistent elevation of beta hCG (see «Diagnosis» below), the condition may also be referred to as gestational trophoblastic neoplasia (GTN).

A placental disease is any disease, disorder, or pathology of the placenta. The article also covers placentation abnormalities, which is often used synonymously for placental disease.

Placental site trophoblastic tumor is a form of gestational trophoblastic disease, which is thought to arise from intermediate trophoblast.

It may secrete human placental lactogen (human chorionic somatomammotropin), and result in a false-positive pregnancy test.

Placental site trophoblastic tumor is a monophasic neoplasm of the implantation site intermediate trophoblast, and usually a benign lesion, which comprises less than 2% of all gestational trophoblastic proliferations. Preceding conditions include molar pregnancy (5%). Compared to choriocarcinoma or invasive mole, hemorrhage is less conspicuous and serum β-HCG level is low, making early diagnosis difficult.

Immunohistochemistry: Often stains with hPL, keratin, Mel-CAM, EGFR.

Prognosis: 10–20% of cases metastase leading to death.

Treatment: Because chemotherapy is ineffective; the patient should undergo hysterectomy.

Trophoblastic neoplasms are neoplasms which derive from trophoblastic tissue.

Examples include:

- choriocarcinoma

- hydatidiform mole

Molar pregnancies usually present with painless vaginal bleeding in the fourth to fifth month of pregnancy. The uterus may be larger than expected, or the ovaries may be enlarged. There may also be more vomiting than would be expected (hyperemesis). Sometimes there is an increase in blood pressure along with protein in the urine. Blood tests will show very high levels of human chorionic gonadotropin (hCG).

Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. It is characterized by "early hematogenous spread" to the lungs. It belongs to the malignant end of the spectrum in gestational trophoblastic disease (GTD). It is also classified as a germ cell tumor and may arise in the testis or ovary.

Choriocarcinoma of the placenta during pregnancy is preceded by:

- hydatidiform mole (50% of cases)

- spontaneous abortion (20% of cases)

- ectopic pregnancy (2% of cases)

- normal term pregnancy (20–30% of cases)

- hyperemesis gravidarum

Rarely, choriocarcinoma occurs in primary locations other than the placenta; very rarely, it occurs in testicles. Although trophoblastic components are common components of mixed germ cell tumors, pure choriocarcinoma of the adult testis is rare. Pure choriocarcinoma of the testis represents the most aggressive pathologic variant of germ cell tumors in adults, characteristically with early hematogenous and lymphatic metastatic spread. Because of early spread and inherent resistance to anticancer drugs, patients have poor prognosis. Elements of choriocarcinoma in a mixed testicular tumor have no prognostic importance.

Choriocarcinomas can also occur in the ovaries.

Molar pregnancy is an abnormal form of pregnancy in which a non-viable fertilized egg implants in the uterus and will fail to come to term.

A molar pregnancy is a gestational trophoblastic disease which grows into a mass in the uterus that has swollen chorionic villi. These villi grow in clusters that resemble grapes. A molar pregnancy can develop when a fertilized egg does not contain an original maternal nucleus. The products of conception may or may not contain fetal tissue. It is characterized by the presence of a hydatidiform mole (or hydatid mole, mola hydatidosa). Molar pregnancies are categorized as partial moles or complete moles, with the word "mole" being used to denote simply a clump of growing tissue, or a "growth".

A complete mole is caused by a single sperm (incidence is about 90%) or two (incidence is about 10%) sperms combining with an egg which has lost its DNA (in the first case the sperm then reduplicates forming a "complete" 46 chromosome set). The genotype is typically 46,XX (diploid) due to subsequent mitosis of the fertilizing sperm, but can also be 46,XY (diploid). 46,YY (diploid) is not observed. In contrast, a partial mole occurs when a haploid egg is fertilized by two sperm or by one sperm which reduplicates itself yielding the genotypes of 69,XXY (triploid) or 92,XXXY (tetraploid). Complete hydatidiform moles have 2 - 4% risk of developing into choriocarcinoma in Western countries and 10 - 15% in Eastern countries and overall, also a 15% chance of becoming an invasive mole. Incomplete moles can become invasive (<5% risk) but are not associated with choriocarcinoma. Complete hydatidiform moles account for 50% of all cases of choriocarcinoma.

Placental villous immaturity, also villous immaturity and villous dysmaturity, is chorionic villous development that is inappropriate for the gestational age.

It is associated with diabetes mellitus

and fetal death near term, i.e. intrauterine demise close to the normal gestational period.

Ovarian pregnancy refers to an ectopic pregnancy that is located in the ovary. Typically the egg cell is not released or picked up at ovulation, but fertilized within the ovary where the pregnancy implants. Such a pregnancy usually does not proceed past the first four weeks of pregnancy. An untreated ovarian pregnancy causes potentially fatal intraabdominal bleeding and thus may become a medical emergency.

Despite their name, germ cell tumors occur both within and outside the ovary and testis.

- head

- inside the cranium — pineal and suprasellar locations are most commonly reported

- inside the mouth — a fairly common location for teratoma

- neck

- mediastinum — account for 1% to 5% of all germ cell neoplasms

- pelvis, particularly sacrococcygeal teratoma

- ovary

- testis

In females, germ cell tumors account for 30% of ovarian tumors, but only 1 to 3% of ovarian cancers in North America. In younger women germ cell tumors are more common, thus in patients under the age of 21, 60% of ovarian tumors are of the germ cell type, and up to one-third are malignant. In males, germ cell tumors of the testis occur typically after puberty and are malignant (testicular cancer). In neonates, infants, and children younger than 4 years, the majority of germ cell tumors are sacrococcygeal teratomas.

Males with Klinefelter syndrome have a 50 times greater risk of germ cell tumors (GSTs). In these persons, GSTs usually contain nonseminomatous elements, present at an earlier age, and seldom are gonadal in location.

Mixed germ cell tumors occur in many forms. Among these, a common form is teratoma with endodermal sinus tumor.

Teratocarcinoma refers to a germ cell tumor that is a mixture of teratoma with embryonal carcinoma, or with choriocarcinoma, or with both. This kind of mixed germ cell tumor may be known simply as a teratoma with elements of embryonal carcinoma or choriocarcinoma, or simply by ignoring the teratoma component and referring only to its malignant component: embryonal carcinoma and/or choriocarcinoma. They can present in the anterior mediastinum.

An interstitial pregnancy is a uterine but ectopic pregnancy; the pregnancy is located outside the uterine cavity in that part of the fallopian tube that penetrates the muscular layer of the uterus. The term cornual pregnancy is sometimes used as a synonym, but remains ambiguous as it is also applied to indicate the presence of a pregnancy located within the cavity in one of the two upper "horns" of a bicornuate uterus. Interstitial pregnancies have a higher mortality than ectopics in general.

Placental villous immaturity, as the name implies, is characterized by chorionic villi that are inappropriately developed for the gestational age. The development and maturation of chorionic villi is essential for normal fetal development.

Immature chorionic villi are larger and have more central blood vessels; thus, the diffusion distance for gas and nutrient exchange is larger and, therefore, placental function is impaired.

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.

Breus' mole (Ova tuberculosa, massive mole) is a massive, subchorionic, tuberous hematoma, formed out of maternal blood in the uterus in pregnancy. It was first described by Karl Breus in 1892.

The symptoms of pseudocyesis are similar to the symptoms of true pregnancy and are often hard to distinguish from it. Such natural signs as amenorrhoea, morning sickness, tender breasts, and weight gain may all be present. Many health care professionals can be deceived by the symptoms associated with pseudocyesis. Research shows that 18% of women with pseudocyesis were at one time diagnosed as pregnant by medical professionals.

The hallmark sign of pseudocyesis that is common to all cases is that the affected patient is convinced that she is pregnant.

Abdominal distension is the most common physical symptom of pseudocyesis (60–90%). The abdomen expands in the same manner as it does during pregnancy so that the affected woman looks pregnant. These symptoms often resolve under general anesthesia and the woman's abdomen returns to its normal size.

The second most common physical sign of pseudocyesis is menstrual irregularity (50–90%). Women are also reported to experience the sensation of fetal movements known as quickening, even though there is no fetus present (50–75%). Other common signs and symptoms include gastrointestinal symptoms, breast changes or secretions, labor pains, uterine enlargement, and softening of the cervix. One percent of women eventually experience false labor.

To be diagnosed as true pseudocyesis, the woman must actually believe that she is pregnant. When a woman intentionally and consciously feigns pregnancy, it is termed a simulated pregnancy.

Symptoms of pseudocyesis can also occur in men who have couvade syndrome.

It is diagnosed by a microscopic examination of the placenta.

Commonly used criteria from Altshuler are: "a minimum of 10 villi, each with 10 or more vascular channels, in 10 or more areas of 3 or more random, non-infarcted placental areas when using a ×10 ocular." The Altshuler criteria are not theoretically rigorous, as they do not define the area. Normal villi have up to five vascular channels.

Endodermal sinus tumor (EST), also known as yolk sac tumor (YST), is a member of the germ cell tumor group of cancers. It is the most common testicular tumor in children under 3, and is also known as infantile embryonal carcinoma. This age group has a very good prognosis. In contrast to the pure form typical of infants, adult endodermal sinus tumors are often found in combination with other kinds of germ cell tumor, particularly teratoma and embryonal carcinoma. While pure teratoma is usually benign, endodermal sinus tumor is malignant.

A Cervical pregnancy is an ectopic pregnancy that has implanted in the uterine endocervix. Such a pregnancy typically aborts within the first trimester, however, if it is implanted closer to the uterine cavity - a so-called cervico-isthmic pregnancy - it may continue longer. Placental removal in a cervical pregnancy may result in major hemorrhage.

It is associated with gestational diabetes, smoking and high altitude.

Clinically, Breus' mole may be asymptomatic, or may present with signs of decreased blood flow to the foetus such as growth restriction and foetal distress. Postnatally, Breus' mole is found in placental examination following live birth or spontaneous abortion. Breus' mole is diagnosed antinatally by ultrasound, where a thick multilobulated hematoma can be seen beneath the chorion. Occasionally, subchorial thrombohematoma may later become intraplacental, making its diagnosis difficult. The mole may be echogenic or hypoechoic depending upon the amount of fresh blood present in it. Breus' mole should be differentiated from vesicular mole and missed abortion in an ultrasound examination.

Some or all of the following symptoms may be present, though it is possible not to experience any symptoms:

- Abdominal pain. Dull aching pain within the abdomen or pelvis, especially during intercourse.

- Uterine bleeding. Pain during or shortly after beginning or end of menstrual period; irregular periods, or abnormal uterine bleeding or spotting.

- Fullness, heaviness, pressure, swelling, or bloating in the abdomen.

- When a cyst ruptures from the ovary, there may be sudden and sharp pain in the lower abdomen on one side.

- Change in frequency or ease of urination (such as inability to fully empty the bladder), or difficulty with bowel movements due to pressure on adjacent pelvic anatomy.

- Constitutional symptoms such as fatigue, headaches

- Nausea or vomiting

- Weight gain

Other symptoms may depend on the cause of the cysts:

- Symptoms that may occur if the cause of the cysts is polycystic ovarian syndrome (PCOS) may include increased facial hair or body hair, acne, obesity and infertility.

- If the cause is endometriosis, then periods may be heavy, and intercourse painful.

The effect of cysts not related to PCOS on fertility is unclear.