Endometrial Stromal Sarcoma: the Zebra in Endometrial Cancers

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The year was 2002. Her journey began with a phone call from her gynecologist. Then came surgery, biopsy, and diagnosis. Her doctor was prepared to propose a treatment. But what in the world is Endometrial Stromal Sarcoma or ESS? No one seemed to know much about it, even her doctor.

When she typed the term on a search engine, she got conflicting information from different sites, but none of them came close to actually discussing the illness. She couldn’t find active discussions or patient advocacy sponsorship groups for ESS, except for a solitary post in a hysterectomy site. She emailed the poster. Finally, she found someone else who has this rare cancer.

What is Endometrial Stromal Sarcoma?

Susan’s story reflects the stories of hundreds of women worldwide suffering from ESS, a relatively rare cancer that affects the endometrium or the lining of the uterus. It’s classified as a sarcoma, one of two known endometrial cancers, the other being adenocarcinoma. Sarcoma is the rarer of the two, making up only 2% of all uterine cancers. Adenocarcinoma makes up more than 80% of cases.

To understand ESS, you need to learn a bit about the uterus, specifically the endometrium. This uterine lining consists of a single-layered epithelium, a protein matrix, tubular glands, and a cell-rich connective tissue called the stroma that supports the glands. While adenocarcinoma attacks the uterine glands and other cells, sarcoma affects the soft tissues, such as the stroma (connective tissue) or the myometrium (muscles in the uterus’ outer part).

There are three types of endometrial sarcomas:

  • Uterine leiomyosarcoma

Soft tissue sarcomas affect smooth muscle tissues, such as those in the abdomen, uterus, and large blood vessels like the inferior vena cava and the pulmonary artery. For uterine leiomyosarcoma, it affects the thick outer layer of muscle.

  • Undifferentiated uterine sarcoma

This rare tumor grows aggressively and accounts for 0.2% of all gynecological malignancies. It doesn’t resemble normal endometrial stroma tissues and has a higher chance of metastasis.

  • Endometrial stromal sarcoma

This malignant tumor resembles normal endometrial stroma but infiltrates the blood vessels or lymph nodes. Low-grade ESS is less aggressive, has a more favorable prognosis, and has a 90% survival rate in 5 years. High-grade ESS shows extensive invasion and common recurrence in less than a year. ESS accounts for less than 1% of all gynecological malignancies.

How do you know you have ESS or cancer of the uterus?

The common symptoms of endometrial stromal sarcoma are prolonged and heavy bleeding and pelvic swelling or pain. Bleeding might occur during menstruation or between cycles, or during and after menopause. In some cases, frequent urinating is a symptom, but this alone is not indicative of ESS. It’s crucial to contact a gynecologist if your menstruation is unusually heavy or became irregular for the first time.

Your doctor may request a screening test or the process of taking an endometrial sample to find out if it has cancer cells. They may also order an MRI to check if your pelvic mass looks like a cancer tumor. Some doctors also conduct an ultrasound in three-month (or regular) intervals to determine if the mass is growing and how fast it grows.

In more severe cases, such as when bleeding doesn’t stop or the mass has grown too large for the uterus, doctors might propose hysterectomy, a surgery performed to remove the uterus. The medical team will likely do a biopsy of the uterus to form a proper cancer of the uterus prognosis and treatment plan.

What can you do when you have ESS?

The stages of uterine cancer often determine the treatment plan. Here are some of the treatment recommendations of gynecologic oncologists:

  • Hormone Therapy

For stage 1 LGESS patients, hormone therapy can work. Medication is based on the illness’s estrogen or progesterone receptors. Hormone therapy may also be given to younger women at pre- or early-stage levels and are planning to have children. As some medicines have side effects that could worsen patients’ treatment experience, knowing your medication options and alternatives is essential. Regular follow-up checkups are also highly recommended.

  • Radiation Therapy


Based on some studies of postoperative adjuvant radiotherapy:

The survival rate is higher for patients with lower ESS staging (stage 1 up to stage 1B) and shallow myometrial invasion than those in higher stages and deeper invasion.

Local control of the disease was better for those who opted for radiation therapy after surgery than those who didn’t, even for HGESS patients.

Radiation therapy works well after surgery, not before it. However, there’s no information to suggest that it is the best treatment for any ESS patient.

  • Hysterectomy or TAH-BSO

If the patient is past childbearing or doesn’t plan to have children, oncologists recommend removing the ‘reproductive organ set’ to eliminate the risks. A hysterectomy removes the uterus and cervix but retains the fallopian tubes and ovaries. A total abdominal hysterectomy with bilateral salpingo-oophorectomy removes the uterus, cervix, ovaries, and tubes.

Lack of Research on Causes and Risks

Almost two decades after Susan and a few other ladies from various continents came together to form a support group for women with ESS, information about this rare cancer remains relatively scarce. Discussion is often combined with other uterine or endometrial cancers that have different characteristics. Thanks to the group, ESS literature isn’t as scant as in 2002, but research is still limited. Treatment plans are still experimental for some, and not many medical facilities and practitioners have the expertise to deal with this specific cancer.

Fortunately, organizations like the Sarcoma Alliance, the American Cancer Society, and CancerCare offer guidance and assistance to ESS survivors and their loved ones. But until research institutions dig deeper into ESS’s causes and risk factors, women will have to wing survival and prevention.

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