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What is undifferentiated embryonal sarcoma of the liver (UESL)?

Undifferentiated embryonal sarcoma of the liver (UESL) is a rare form of liver cancer that occurs mainly in children, usually between ages 5 and 10, but also well into adolescence. It is the third most common type of primary liver cancer in kids, after hepatoblastoma and hepatocellular carcinoma. Although UESL is an aggressive cancer, treatment options — including intensive chemotherapy and surgery — can be curative.

Undifferentiated Embryonal Sarcoma of the Liver | Symptoms & Causes

What are symptoms of UESL?

UESL doesn’t always cause symptoms. When it does, children may experience:

What causes undifferentiated embryonal sarcoma of the liver?

The cause of UESL is still unknown.

Undifferentiated Embryonal Sarcoma of the Liver | Diagnosis & Treatments

How is undifferentiated embryonal sarcoma of the liver diagnosed?

If your child’s physician suspects UESL, they will conduct a physical exam and ask questions about your child’s medical history and symptoms. They will also order certain tests, which may include:

Based on the results of these tests, they may also perform a biopsy to learn more about the tumor and determine whether it is cancerous. These tumors are thought to arise from benign cystic lesions in the liver and can have both solid and cystic components. For that reason, your child’s physician should plan carefully to make sure that they biopsy the appropriate area of the tumor. We prefer a needle biopsy over an open biopsy. Because the cells in these tumors can appear unusual under the microscope, a skilled pathologist should diagnose UESL.

How is UESL treated?

Your child’s physician will determine the specific treatment for UESL, based on some or all of the following factors:

  • your child’s age, overall health, and medical history
  • extent of the disease
  • your child’s tolerance for specific medications, procedures, and therapies
  • how your child’s physicians expect the disease to progress
  • your opinion or preference

Children and teens with UESL will need both chemotherapy and surgery to achieve a cure. UESL is often quite responsive to chemotherapy. However, the disease is more difficult to treat if it has spread outside of the liver.


Most children diagnosed with UESL require treatment with chemotherapy. Chemotherapy works by interfering with the cancer cells’ ability to grow or reproduce.

  • Chemotherapy enters the bloodstream and then travels throughout the body to kill cancer cells.
  • Different groups of chemotherapy drugs work in different ways to fight cancer cells and shrink tumors.
  • Often, a combination of chemotherapy drugs is used.

While chemotherapy can be quite effective in treating certain cancers, these drugs can’t tell the difference between normal healthy cells and cancer cells. Because of this, your child may experience side effects during treatment. We assign each family a comprehensive team of providers, including a primary attending physician, a primary fellow or trainee, a nurse practitioner, a primary nurse, and a psychosocial provider. Together, we can help you and your child prepare for side effects and, in some cases, prevent, them from occurring.


In addition to medical therapies, surgery is a necessary part of therapy for all liver tumors, including UESL. Surgery may involve removing a portion of the liver (partial hepatectomy), or in rare cases, the entire liver (total hepatectomy), replacing it with a liver from an organ donor (liver transplant).

Surgery involving the liver is very complex and requires an experienced surgeon. Because liver tumors in children are rare, it’s important that liver surgeries be performed by surgeons with unique and deep expertise in liver tumor resections. Our experts specialize in pediatric liver surgery and have successfully performed some of the most complicated liver operations in children.

Within the past 20 years, our surgeons have performed more than 120 liver resections and more than 35 liver transplants, as well as three multivisceral transplants for children with liver tumors. We offer the most advanced and aggressive surgical techniques available including:

  • transjugular and conventional interventionally guided liver biopsies
  • ex vivo resection with autotransplantation (removing the liver to allow dissection of an advanced tumor from the organ, while replacing the remaining liver following removal of the cancer)
  • blood-vessel or bile-duct reconstruction
  • heart-lung bypass to remove a tumor that has grown into the heart
  • use of indocyanine green (ICG) to illuminate tumors and guide resection
  • advanced imaging techniques (MRI with Eovist, MRCP, PET/CT)
  • interventional radiology procedures (TACE, Y-90) as a bridge to surgical resection.

Very few pediatric hospitals in the United States offer these procedures.

How we care for UESL at Boston Children’s Hospital

We treat children with UESL in the Liver Tumor Center at the Dana-Farber/Boston Children’s Cancer and Blood Disorders Center. We have some of the most experienced pediatric liver cancer oncologists and surgeons in the world, as well as internationally recognized pediatric subspecialists who use sophisticated technology and therapies to maximize outcomes for our patients.

Undifferentiated Embryonal Sarcoma of the Liver | Programs & Services