Uterine sarcoma are rare, out of all malignancies of the uterine body only about 4% will be uterine sarcomas. Generally, the cause of the lesion is not known, however patients with a history of pelvic radiation are at higher risk. Most tumors occur after menopause.

Women who take long-term tamoxifen are at higher risk.

The risk of a repeat GTD is approximately 1 in 100, compared with approximately 1 in 1000 risk in the general population. Especially women whose hCG levels remain significantly elevated are at risk of developing a repeat GTD.

Sarcoma botryoides normally is found in children under 8 years of age. Onset of symptoms occurs at age 3 years (38.3 months) on average. Cases of older women with this condition have also been reported.

Most women with GTD can become pregnant again and can have children again. The risk of a further molar pregnancy is low. More than 98% of women who become pregnant following a molar pregnancy will not have a further hydatidiform mole or be at increased risk of complications.

In the past, it was seen as important not to get pregnant straight away after a GTD. Specialists recommended a waiting period of 6 months after the hCG levels become normal. Recently, this standpoint has been questioned. New medical data suggest that a significantly shorter waiting period after the hCG levels become normal is reasonable for approximately 97% of the patients with hydatidiform mole.

The disease used to be uniformly fatal, with a 5-year survival rate between 10 and 35%. As a result, treatment was radical surgery. New multidrug chemotherapy regimens with or without radiation therapy are now used in combination with less radical surgery with good results, although outcome data are not yet available.

The uterine sarcomas form a group of malignant tumors that arises from the smooth muscle or connective tissue of the uterus.

Uterine cancer resulted in about 58,000 deaths in 2010 up from 45,000 in 1990.

Uterine cancer is the fourth most common cancer in women in the UK (around 8,500 women were diagnosed with the disease in 2011), and it is the tenth most common cause of cancer death in women (around 2,000 people died in 2012).

A malignant mixed Müllerian tumor, also known as malignant mixed mesodermal tumor, MMMT and carcinosarcoma, is a malignant neoplasm found in the uterus, the ovaries, the fallopian tubes and other parts of the body that contains both carcinomatous (epithelial tissue) and sarcomatous (connective tissue) components. It is divided into two types, homologous (in which the sarcomatous component is made of tissues found in the uterus such as endometrial, fibrous and/or smooth muscle tissues) and a heterologous type (made up of tissues not found in the uterus, such as cartilage, skeletal muscle and/or bone). MMMT account for between two and five percent of all tumors derived from the body of the uterus, and are found predominantly in postmenopausal women with an average age of 66 years. Risk factors are similar to those of adenocarcinomas and include obesity, exogenous estrogen therapies, and nulliparity. Less well-understood but potential risk factors include tamoxifen therapy and pelvic irradiation.

The terms uterine cancer and womb cancer may refer to any of several different types of cancer which occur in the uterus, namely:

- Endometrial cancer:

- Cervical cancer arises from the transformation zone of the cervix, the lower portion of the uterus and connects to the upper aspect of the vagina.

- Uterine sarcomas: sarcomas of the myometrium, or muscular layer of the uterus, are most commonly leiomyosarcomas.

- Gestational trophoblastic disease relates to neoplastic processes originating from tissue of a pregnancy that often is located in the uterus.

More than 80% of hydatidiform moles are benign. The outcome after treatment is usually excellent. Close follow-up is essential. Highly effective means of contraception are recommended to avoid pregnancy for at least 6 to 12 months.

In 10 to 15% of cases, hydatidiform moles may develop into invasive moles. This condition is named "persistent trophoblastic disease" (PTD). The moles may intrude so far into the uterine wall that hemorrhage or other complications develop. It is for this reason that a post-operative full abdominal and chest x-ray will often be requested.

In 2 to 3% of cases, hydatidiform moles may develop into choriocarcinoma, which is a malignant, rapidly growing, and metastatic (spreading) form of cancer. Despite these factors which normally indicate a poor prognosis, the rate of cure after treatment with chemotherapy is high.

Over 90% of women with malignant, non-spreading cancer are able to survive and retain their ability to conceive and bear children. In those with metastatic (spreading) cancer, remission remains at 75 to 85%, although their childbearing ability is usually lost.

There is debate over the naming of MMMT; the term carcinosarcoma was formerly used to describe lesions with homologous tumors, and "malignant mixed Müllerian tumor" or "mixed mesodermal tumor" was used to describe heterologous tumors. While "carcinosarcoma" now considered standard, "malignant mixed Müllerian tumor" has a lengthy history within gynecological literature and is expected to continue to be used. The naming issue to a certain extent reflects histological characteristics and development of the tumors, in which the different types of tissues are believed to either develop separately and join into a single mass (the "collision" theory), that an adenocarcinoma stimulates the stroma to create a tumor (the "composition" theory), or that the tumor is the result of a stem cell that differentiates into different cell types (the "combination" theory). "Collision" tumors are normally easily recognized and not considered true MMMTs; the "combination" theory is most widely held, and is due to evidence that the tumors develop from a single line of cells, developing in a fashion similar to the fundus of the uterus from the Müllerian duct - first from a stem cell into a population of cells, that then differentiates into epithelial and stromal components.

There is evidence that some tumors are better explained by the composition theory, due to the aggressive nature of the epithelial cells involved which tend to metastasize much more readily than the sarcomal component. The behavior of MMMT overall is more related to the type and grade of the epithelium than the sarcoma, which suggests the sarcomal portion is an atypical "bystander" than primary driver of the tumor. Despite this, when purely endometrial tumors are compared to MMMTs, the MMMT tumor tends to have a worse prognosis.

Most soft-tissue sarcomas are not associated with any known risk factors or identifiable cause. There are some exceptions:

- Studies suggest that workers who are exposed to chlorophenols in wood preservatives and phenoxy herbicides may have an increased risk of developing soft-tissue sarcomas. An unusual percentage of patients with a rare blood vessel tumor, angiosarcoma of the liver, have been exposed to vinyl chloride in their work. This substance is used in the manufacture of certain plastics, notably PVC.

- In the early 1900s, when scientists were just discovering the potential uses of radiation to treat disease, little was known about safe dosage levels and precise methods of delivery. At that time, radiation was used to treat a variety of noncancerous medical problems, including enlargement of the tonsils, adenoids, and thymus gland. Later, researchers found that high doses of radiation caused soft-tissue sarcomas in some patients. Because of this risk, radiation treatment for cancer is now planned to ensure that the maximum dosage of radiation is delivered to diseased tissue while surrounding healthy tissue is protected as much as possible.

- Kaposi's sarcoma, a rare cancer of the cells that line blood vessels in the skin and mucus membranes, is caused by Human herpesvirus 8. Kaposi's sarcoma often occurs in patients with AIDS (acquired immune deficiency syndrome). Kaposi's sarcoma, however, has different characteristics than typical soft-tissue sarcomas and is treated differently.

- In a very small fraction of cases, sarcoma may be related to a rare inherited genetic alteration of the p53 gene and is known as Li-Fraumeni syndrome. Certain other inherited diseases are associated with an increased risk of developing soft-tissue sarcomas. For example, people with neurofibromatosis type I (also called von Recklinghausen's disease, associated with alterations in the NF1 gene) are at an increased risk of developing soft-tissue sarcomas known as malignant peripheral nerve sheath tumors. Patients with inherited retinoblastoma have alterations in the RB1 gene, a tumor suppressor gene, and are likely to develop soft-tissue sarcomas as they mature into adulthood.

Adenomatoid tumor is a benign mesothelial tumor, which arises from the lining of organs. It generally presents in the genital tract, in regions such as the testis and epididymis. It is the second most common extratesticular scrotal mass, after lipoma, and accounts for 30% of these masses. It also has been found in the pancreas.

In the female, it has been found in the body of the uterus and the fallopian tube.

Surgery, with as wide a margin of removal as possible, has generally been the most effective and preferred way to attack LMS. If surgical margins are narrow or not clear of tumor, however, or in some situations where tumor cells were left behind, chemotherapy or radiation has been shown to give a clear survival benefit. While LMS tends to be resistant to radiation and chemotherapy, each case is different and results can vary widely.

LMS of uterine origin do frequently, but not always respond to hormonal treatments.

Compared to other breeds of dog, Scottish terriers have a much increased risk of developing transitional cell carcinoma.

Childhood rhabdomyosarcoma has been fatal. Recovery rates have increased by 50 percent since 1975. In children five years of age or younger survival rates are up to 65 percent. In adolescents younger than 15 years old, the survival rate has increased up to 30 percent.

Invasive hydatidiform mole, also known as invasive mole and chorioadenoma destruens is a type of neoplasia that grows into the muscular wall of the uterus. It is formed after conception (fertilization of an egg by a sperm). It may spread to other parts of the body, such as the vagina, vulva, and lung.

The prognosis for rhabdomyosarcoma has improved greatly in recent decades, with over 70% of patients surviving for five years after diagnosis.

Soft-tissue sarcomas are relatively uncommon cancers. They account for less than 1% of all new cancer cases each year. This may be because cells in soft tissue, in contrast to tissues that more commonly give rise to malignancies, are not continuously dividing cells.

In 2006, about 9,500 new cases were diagnosed in the United States. Soft-tissue sarcomas are more commonly found in older patients (>50 years old) although in children and adolescents under age 20, certain histologies are common (rhabdomyosarcoma, synovial sarcoma).

Around 3,300 people were diagnosed with soft tissue sarcoma in the UK 2011.

The cause of this condition is not completely understood. Potential risk factors may include defects in the egg, abnormalities within the uterus, or nutritional deficiencies. Women under 20 or over 40 years of age have a higher risk. Other risk factors include diets low in protein, folic acid, and carotene. The diploid set of sperm-only DNA means that all chromosomes have sperm-patterned methylation suppression of genes. This leads to overgrowth of the syncytiotrophoblast whereas dual egg-patterned methylation leads to a devotion of resources to the embryo, with an underdeveloped syncytiotrophoblast. This is considered to be the result of evolutionary competition with male genes driving for high investment into the fetus versus female genes driving for resource restriction to maximise the number of children.

Embryonal rhabdomyosarcoma (ERMS) is a rare histological form of cancer of connective tissue wherein the mesenchymally-derived malignant cells resemble the primitive developing skeletal muscle of the embryo. It is the most common soft tissue sarcoma occurring in children.

Pregnancies in a bicornuate uterus are usually considered high risk and require extra monitoring because of association with poor reproduction potential.

A bicornuate uterus is associated with increased adverse reproductive outcomes, such as:

- Recurrent pregnancy loss

- Preterm birth: The rate of preterm delivery is 15 to 25%. A pregnancy may not reach full term in a bicornuate uterus when the baby begins to grow in either of the uterine horns. A short cervical length seems to be a good predictor of preterm delivery in women with a bicornuate uterus.

- Malpresentation (breech birth or transverse presentation): a breech presentation occurs in 40-50% of pregnancies with a partial bicornuate uterus and not at all (0%) in a complete bicornuate uterus.

- Deformity: Offspring of mothers with a bicornuate uterus are at high risk for "deformities and disruptions" and "malformations."

Previously, a bicornuate uterus was thought to be associated with infertility, but recent studies have not confirmed such an association.

The occurrence of all types of paramesonephric duct abnormalities in women is estimated around 0.4%.

A bicornuate uterus is estimated to occur in 0.1-0.5% of women in the U.S.

It is possible that this figure is an underestimate, since subtle abnormalities often go undetected. Some intersex individuals whose external genitalia are perceived as being male may nonetheless have a variably shaped uterus.

Sarcomas are quite rare with only 15,000 new cases per year in the United States. Sarcomas therefore represent about one percent of the 1.5 million new cancer diagnoses in that country each year.

Sarcomas affect people of all ages. Approximately 50% of bone sarcomas and 20% of soft tissue sarcomas are diagnosed in people under the age of 35. Some sarcomas, such as leiomyosarcoma, chondrosarcoma, and gastrointestinal stromal tumor (GIST), are more common in adults than in children. Most high-grade bone sarcomas, including Ewing's sarcoma and osteosarcoma, are much more common in children and young adults.

Patients who have been diagnosed with ARMS often have poor outcomes. The four year survival rate without remission for local ARMS tumors is 65 percent, while the four year survival rate with metastatic ARMS is only 15 percent. Patients who have metastatic ARMS positive with PAX3-FOXO1 fusion often have a poorer outcome than patients positive with PAX7-FOXO1 fusion, with a four-year survival rate of 8 percent and 75 percent respectively. Other variables affect the four year survival rate, such as, primary tumor site, size of primary tumor, amount of local invasion, number of distal lymph nodes spread to, and whether metastasis has occurred. Prognosis for patients who have primary tumor sites within the bones often have higher survival rates and respond well to treatment options. While patients who have primary tumor sites within the nasopharynx region with metastases to the breast have very poor outcomes. Patients who are fusion protein negative with low risk clinical features should be treated with reduced therapy, while patients who are fusion protein positive with low risk clinical features should be treated as an intermediate risk and have more intensive therapy regimens.