Uterine leiomyosarcoma is a rare form of cancer. The earlier uterine leiomyosarcoma is diagnosed, the better the outlook.

Uterine leiomyosarcoma accounts for 2–5% of all uterine cancers. It starts in the muscle lining the walls of the uterus.

The condition is often difficult to treat as it can grow quickly, spread quickly, and be resistant to some forms of treatment.

Symptoms can be similar to other noncancerous uterine conditions.

Other possible, but rare, symptoms include:

Doctors still don’t know what specifically causes uterine leiomyosarcoma.

What is known is that it tends to occur around the time of menopause, whether that’s before or after.

The average age of people affected is around 50 years old.

A doctor will usually perform a physical examination and be able to feel a uterine mass or more than one mass. But it’s very difficult for them to tell whether the mass (generally a fibroid) is benign or cancerous.

Often, it’s assumed the mass is benign as uterine leiomyosarcoma is rare, so biopsies typically aren’t taken. Only when the mass is surgically removed is cancer usually diagnosed.

According to a 2011 review, only around 0.5% of uterine fibroid cases that require surgery turns out to be leiomyosarcoma.

Uterine leiomyosarcoma is split into four stages, ranging from Stage 1 to Stage 4. The higher the number, the more cancer has spread and the more difficult it usually is to treat.

These are then further split into sub-stages.

Stage 1 means the cancer is only located inside the uterus:

  • Stage 1A is for a tumor that’s 5 centimeters in size or smaller
  • Stage 1B is for a tumor that’s larger than 5 centimeters

Stage 2 is used when cancer has spread outside of the uterus but not beyond the pelvic area:

  • Stage 2A: cancer has spread to the ovaries, fallopian tubes, or tissues surrounding the uterus
  • Stage 2B: cancer has spread to other pelvic tissues

Stage 3 sees cancer inside abdominal tissues:

  • Stage 3A: cancer has spread to just one abdominal location
  • Stage 3B: cancer has spread to more than one abdominal area
  • Stage 3C: cancer has spread to lymph nodes in or around the pelvic and abdominal areas

Stage 4 is the highest stage of uterine leiomyosarcoma and is used when cancer has spread to more distant areas:

  • Stage 4A is for a tumor that’s spread into the rectum or bladder (or both)
  • Stage 4B means cancer has spread to parts of the body that are distant from the original location (the uterus)

If cancer remains inside the uterus (Stage 1), surgery to remove it and the uterus via a hysterectomy may be the only treatment needed.

For more advanced stages, doctors may recommend surgery to remove other parts of the body such, as the ovaries or fallopian tubes, along with the uterus.

Additional treatments like chemotherapy or radiotherapy may also be offered. In some cases, these treatments may be the only options available for people who aren’t well enough for surgery.

These adjunctive treatments haven’t yet shown they can help people live longer, but they can reduce the chance of cancer recurring in certain areas.

As uterine leiomyosarcoma can be difficult to treat, newer types of treatments like immunotherapy and targeted drug therapy may be considered, too — particularly when other therapies are ineffective.

The earlier uterine leiomyosarcoma is diagnosed, the better the outlook. Around 60% of people with this form of cancer are diagnosed at an early stage.

According to a review published in 2017, 75.8% of people with Stage 1 uterine leiomyosarcoma survive at least 5 years after treatment free from cancer.

This reduces to 60.1% for Stage 2, 44.9% for Stage 3, and 28.7% for Stage 4.

This cancer is typically aggressive and harder to treat than other types, regardless of the stage. There’s also a significant chance of cancer recurring after treatment, even in the early stages.

Ultimately, doctors are still trying to find the most effective treatment for this rare cancer.

Lauren Sharkey is a U.K.-based journalist and author specializing in women’s issues. When she isn’t trying to discover a way to banish migraines, she can be found uncovering the answers to your lurking health questions. She has also written a book profiling young female activists across the globe and is currently building a community of such resisters. Catch her on Twitter.