Endometrial stromal sarcoma (ESS) is a rare, malignant tumor that forms in the uterine lining. Doctors most commonly diagnose it in people in the perimenopause stage.

ESS is a subtype of a rare form of uterine cancer called uterine sarcoma. In comparison with endometrial cancer, uterine sarcoma makes up approximately 0.2 to 1% of uterine cancers.

First-line treatment for endometrial stromal sarcoma involves surgery to remove the uterus. Doctors may also recommend targeted drug therapies, chemotherapy, and radiation.

This article discusses the symptoms, risk factors, and treatments for ESS.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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ESS grows inside the endometrium of the uterus on tissue called the stroma. Doctors can classify these atypical changes to the stroma as:

  • Low-grade ESS (LG-ESS): In a pathology report, LG-ESS describes worm-like, stromal cell changes that possibly grow into the uterine muscle wall and pelvic lymph nodes. It is less aggressive, spreads slowly, and has a more favorable prognosis.
  • High-grade ESS (HG-ESS): In a pathology report, HG-ESS describes significant stromal cell changes that have divided more quickly and possibly already spread outside the uterus. It is aggressive to treat — individuals are often at stage 3 or 4 of the disease at the time of diagnosis.

Uterine sarcoma is one of two types of uterine cancer. Healthcare professionals classify it into four subtypes according to which part of the uterus the cancer cells spread. The subtypes include:

  • endometrial stromal nodule
  • uterine leiomyosarcoma
  • endometrial stromal sarcoma
  • undifferentiated sarcoma

ESS is the second most common type of uterine sarcoma. Both LG-ESS and HG-ESS have a high rate of recurrence, as the optimal treatment strategies for the disease remain a matter of debate among some healthcare experts. However, many doctors recommend surgery with a total hysterectomy.

Although less common, some people with undiagnosed ESS may not experience symptoms. Those who do report symptoms may notice the following:

  • atypical uterine bleeding
  • pelvic pain
  • pain with urination
  • pelvic masses that seem to grow bigger

Additionally, because the symptoms of ESS overlap with noncancerous conditions, such as fibroids, adenomyosis, and endometrial polyps, doctors can often misdiagnose the condition.

If a person has vaginal bleeding outside of menstruation, their doctor may want to rule out ESS. Spotting and bleeding changes around perimenopause can also create uncertainty. A person can talk with a doctor about new or worsening vaginal bleeding to be sure.

A doctor will likely perform multiple tests according to a patient’s symptoms to diagnose ESS or suspected recurrent ESS. Diagnostic testing and tissue sampling could include:

  • transvaginal ultrasound, an ultrasound scan using an internal probe
  • hysteroscopy, when doctors insert a thin scope into the uterus through the vagina
  • endometrial biopsy or dilation and curettage
  • CT, PET, or MRI scans of the abdomen or chest

While doctors do not know what causes ESS, scientific research has identified certain risk factors.

A person’s risk of developing the disease seems to increase in association with the following:

  • obesity
  • diabetes
  • polycystic ovary syndrome
  • endometrial hyperplasia, a condition that causes the uterine lining to become thicker
  • an enlarged uterus
  • elevated estrogen levels
  • former or current use of tamoxifen
  • endometriosis, when tissue resembling uterine tissue develops in other areas of the body
  • adenomyosis, when the cells of the uterine lining grow into the muscular wall of the uterus

Health experts do not know whether having a family member with ESS increases a child’s risk of developing uterine sarcoma. However, most patients with an ESS diagnosis do not have a family history.

Doctors consider ESS a rare tumor because it makes up almost less than 1% of all uterine cancers.

Most women have an average age of 45–55 years at diagnosis, but researchers have reported isolated cases of the disease in women under 40 years. More than 50% of women with an LG-ESS diagnosis are in perimenopause.

Results from the Surveillance, Epidemiology, and End Results database, which tracks demographic data about cancer statistics, indicate that uterine sarcoma appears in Black women two times more often than in white women. However, experts have not determined exactly why this is the case.

Treatment for ESS depends on a person’s age, their fertility concerns, and whether their ESS is high or low grade. However, for both HG-ESS and LG-ESS, surgery with a total hysterectomy is the standard treatment to remove stromal sarcoma cells and signs of metastasis.

A surgeon will also likely perform a bilateral salpingo-oophorectomy to remove both ovaries and fallopian tubes, along with a pelvic lymphadenectomy to remove lymph nodes.

Fertility-sparing management is possible for those with LG-ESS who may want to become pregnant in the future. Due to the high rate of recurrence of ESS, however, researchers argue that this should only become an option after meeting with a gynecological oncologist to discuss the risks.

Following surgery, a doctor may recommend additional therapies, such as estrogen blockers, targeted drug therapies, radiation, or chemotherapy.

Since ECC is rare, research on the best course of treatment is ongoing. A person with the disease should consult a doctor to understand the benefits and drawbacks of specific treatments.

The prognosis for LG-ESS is more favorable than for HG-ESS. If the cancer has not spread beyond the uterus, treatment may cure LG-ESS.

The 5-year survival rate for stages 1 and 2 is 90% and 50% for stages 3 and 4. However, both LG-ESS and HG-ESS have a high rate of recurrence, which refers to the cancer returning.

The survival rate of HG-ESS is over 19 months, depending on the course of treatment and how much the disease has spread.

An endometrial stromal sarcoma is a rare form of uterine cancer that begins in the connective tissue of the uterus. The most common symptom is heavy vaginal bleeding outside menstruation and after menopause.

A doctor will recommend surgery to remove the uterus and nearby organs. Treatment options depend on a person’s age, desire for future pregnancy, and whether the sarcoma cells are low- or high-grade.