Myeloid Sarcoma

What is myeloid sarcoma?

Myeloid sarcoma, also known as chloroma, is a rare cancerous tumor most commonly diagnosed in people with acute myeloid leukemia (AML). Unlike other blood cancers — including AML — myeloid sarcoma forms outside your bone marrow. Your bone marrow is the spongy tissue in your bones that makes your body's blood cells, including:

• White blood cells.
• Red blood cells.
• Platelets.

With AML, abnormal white blood cells called myeloblasts form in your bone marrow. These cells can spill out and travel through your bloodstream. Similarly, myeloid sarcomas contain myeloblasts. However, these tumors appear most commonly in your lymph nodes, soft tissues, skin, testes, gastrointestinal tract and your abdomen's lining (peritoneum).

Myeloid sarcoma goes by different names:

• Chloroma: Myeloid sarcoma often contains an enzyme (myeloperoxidase) that makes its cells appear green under a microscope. "Chlor" comes from a Greek word that means green. "Oma" means a tumor or cancer.
• Granulocytic sarcoma: Granulocytes are a specific kind of mature white blood cell. Some myeloid cells that turn cancerous (myeloblasts) are precursors to granulocytes.
• Extramedullary myeloid tumor: "Extramedullary" means outside of the bone marrow. Unlike most blood cancers, myeloid sarcoma forms masses of leukemia cells outside of the bone marrow.

Is myeloid sarcoma a blood cancer?

Myeloid sarcoma is a blood cancer. However, imagining myeloid sarcoma as a blood cancer can be confusing because it's not found where blood cancer forms — in bone marrow. Also, most blood cancers don't involve tumors.

It's helpful to think of myeloid sarcoma in terms of its components. Although it's a solid soft tissue mass, it contains the same type of cancer cells associated with AML and some other types of blood cancers. Related, it responds to treatments that work best for blood-related cancers.

Who does it affect?

Myeloid sarcoma can affect people of any age or gender, but it’s most common in adults. You’re more likely to develop myeloid sarcoma if you have AML, but people without AML develop myeloid sarcoma in rare cases. A myeloid sarcoma that forms outside of an AML diagnosis is called a primary myeloid sarcoma.

How common is myeloid sarcoma?

Myeloid sarcoma is rare, affecting anywhere from 2.5% to 9.1% of people diagnosed with AML. While AML is one of the most common types of leukemia in adults, it’s rare, too, making up only 1% of cancer diagnoses each year in the U.S. Myeloid sarcoma is even rarer among people without an AML diagnosis (primary myeloid sarcoma). About 2 out of 1 million adults without an AML diagnosis have myeloid sarcoma.

What causes myeloid sarcoma?

Myeloid sarcoma forms when myeloid cells — the cells that normally mature into healthy blood cells — become cancer cells instead. A genetic mutation (change) happens that causes myeloid cells to become immature white blood cells called myeloblasts. These cells become a tumor that can form anywhere in your body, damaging nearby tissue.

Researchers aren't sure what causes the mutation to happen. They're also unsure why myeloid sarcoma forms outside the bone marrow, unlike related blood cancers.

Who is at risk of developing myeloid sarcoma?

You're most likely to develop myeloid sarcoma if you have a history of acute myeloid leukemia or related blood cancers. People at risk include those:

• Who currently have AML.
• With AML that's in remission (myeloid sarcoma can be a sign that cancer has returned).
• With chronic myeloid leukemia (CML).
• With myeloproliferative neoplasms.
• With myelodysplastic syndrome.

In people with primary myeloid sarcoma, the tumor may be the first sign of AML.

What are the symptoms of myeloid sarcoma?

There aren't common symptoms because myeloid sarcomas can form anywhere outside the blood marrow and affect various organs or tissues. Any symptoms you experience with myeloid sarcoma are likely related to the tumor's size and whether it's impacting a nearby organ.

Common symptoms are nonspecific but may include general symptoms like fatigue, weight loss, loss of appetite or pain, among others, depending on where the myeloid sarcoma develops.

How is myeloid sarcoma diagnosed?

Your provider will monitor you carefully for myeloid sarcoma if you have AML. It's harder to diagnose myeloid sarcoma without this medical history because these tumors are rare. Providers don't always know to look for them. It's easy to mistake myeloid sarcoma for more common tumors.

An important part of the diagnostic workup involves ruling out common tumors or other lesions. The only way to confirm a diagnosis is to examine the tumor cells closely in a lab.

Your provider may recommend any of the following procedures:

• CT scan and MRI: A CT scan and MRI can rule out abnormalities that may be mistaken for myeloid sarcomas, like more common benign or cancerous tumors or abscesses. An abscess is a collection of fluid, like pus. An MRI is especially beneficial when identifying tumors affecting your brain or spinal cord.
• PET scan: A PET scan allows your provider to pinpoint the tumor's exact location. It can also show if you have additional tumors. Your provider may also order a PET scan to plan for radiation therapy treatment or see how your tumor responds to treatment.
• Core biopsy: An X-ray-guided core biopsy allows your provider to remove a portion of your tumor so that it can be tested in a lab for cancer cells. Examining the cells up close is the only way to know if your tumor is a myeloid sarcoma. Testing the cells in a lab can also help your provider determine what treatments may work best.
• Ultrasound: Providers typically use ultrasound as the main way to diagnose myeloid sarcoma of the testes.

What tests will be done to diagnose this condition?

Tests may include:

• Cytogenetic analysis: This test examines cells to look for damaged chromosomes. Chromosomes contain the genetic code (DNA) that tells a cell how to behave. Researchers can identify myeloid sarcoma based on abnormalities in the chromosomes.
• Immunophenotyping: This test looks for specific antigens or markers (certain enzymes or proteins) on the biopsied cells to determine the type of cancer.
• Biopsy: A biopsy is the removal of some cells or tissue, fluids or growths for examination. Your provider will likely perform a biopsy and send it to a laboratory for testing to confirm the diagnosis.
• Bone marrow biopsy: In a bone marrow biopsy, a provider or medical technician removes a small sample of bone marrow from inside your bone. The sample is usually taken from your pelvic bone, although it’s occasionally taken from your breastbone. Your provider may order this test to see if there’s concomitant AML or if the myeloid sarcoma is solitary/localized.

How is myeloid sarcoma treated?

Treatments for myeloid sarcoma and AML are similar. The specific therapies (or combination of therapies) depend on various factors, including the tumor's location and size, genetic abnormalities in the tumor cells, your age, health and whether you have a co-occurring condition, like AML.

Your provider may recommend:

• Chemotherapy: Chemotherapy is the most effective treatment for myeloid sarcoma and usually starts immediately after your diagnosis. It uses drugs to kill cancer cells or stop them from multiplying. Chemotherapy used to treat myeloid sarcoma kills your tumor's cancer cells and targets cancer cells outside your tumor, too.
• Surgery: Your provider may recommend removing the tumor. Surgery can help with symptom relief if the sarcoma impacts a nearby organ. Surgery alone doesn't stop the cancer cells from growing, however. You'll need chemotherapy along with surgery to stop the cancer cells.
• Radiation therapy: Like surgery, radiation can be combined with chemotherapy. Radiation uses energy beams, like X-rays, to shrink the tumor. You may receive radiation depending on where the tumor forms and/or if the tumor isn't responding to chemotherapy alone. You may also receive radiation if cancer goes away but returns (remission) after a stem cell transplant. Radiation can help relieve symptoms, too.
• Allogeneic hematopoietic stem cell transplant: During an allogeneic stem cell transplant, you receive healthy stem cells from a donor. These stem cells eventually grow into healthy blood cells. They replace the cancer cells. Transplants usually occur during remission (when there's no sign of cancer) and after chemotherapy treatments.
• Targeted therapy: This treatment uses drugs designed to attack weaknesses in cancer cells so that they die or are no longer able to multiply.

How can I prevent myeloid sarcoma?

Myeloid sarcoma is so rare that scientists haven't gathered enough information yet to know how to prevent it.

What is the survival rate of myeloid sarcoma?

Myeloid sarcoma, like AML, is a fast-growing cancer. Without treatment, it can progress quickly, leading to death. However, studies have shown that treatment can slow the progression of myeloid sarcoma, and there’s the potential to put the cancer in remission, a state where your provider can’t identify active cancer on testing. A cure is difficult, but it’s possible and depends on many factors, including how your body responds to treatments. Research has also shown that treatments can help you live longer with a myeloid sarcoma diagnosis.

Your outcomes depend on many factors. These factors include whether you have primary myeloid sarcoma or myeloid sarcoma with AML, your age, your response to chemotherapy, etc. Talk to your provider about how your health and diagnosis will shape your unique treatment outcomes.

What questions should I ask my doctor?

You may want to ask your healthcare provider:

• What types of symptoms should I expect?
• What is the likelihood the sarcoma will progress to AML?
• What are my treatment options?
• What are the treatment risks and side effects?
• How can I manage treatment side effects?
• What type of follow-up care do I need after treatment?
• Should I look out for signs of complications?

A note from Cleveland Clinic

Myeloid sarcoma, like AML, is a fast-growing cancer that often requires aggressive treatment. It’s difficult to cure, but finding the right therapies can slow myeloid sarcoma’s growth and possible progression to AML, if it’s not already present. The right treatments can also put your cancer into remission. Your provider will monitor you closely in case the cancer returns. Ask your provider about the best care plan for your cancer based on your unique case.