Myxofibrosarcoma

Myxofibrosarcoma is a type of cancer that starts in the connective tissue, most commonly appearing as a slow-growing lump in the arms or legs. This cancer primarily affects older adults and has a tendency to return even after treatment, making careful monitoring essential for those diagnosed with this condition.

Table of contents

• What is myxofibrosarcoma?
• Signs and symptoms
• Causes and risk factors
• How doctors diagnose this condition
• Cancer grading and staging
• Treatment options
• Outlook and recurrence

What is myxofibrosarcoma?

Myxofibrosarcoma is a type of cancer that begins in the connective tissue, which is the material that connects, supports, and surrounds other body structures like bones, muscles, and organs^[1]. This cancer typically grows in the connective tissues beneath the skin, though less often it can grow in deeper tissues surrounding muscles^[2].

This condition is one of the most common types of soft tissue sarcoma (a cancer that happens in soft tissues) in adults, particularly affecting the arms and legs^[3]. Myxofibrosarcoma most often starts in the leg and rarely begins in the abdomen, where other kinds of sarcomas tend to grow^[1]. In England, there are an average of 178 cases diagnosed every year, making up about 4.5% of all soft tissue sarcomas^[6].

The estimated incidence of myxofibrosarcoma is less than 0.1 per 100,000 each year^[3]. While it is considered an aggressive cancer that can spread to other parts of the body and often returns after treatment, individual experiences vary greatly depending on many factors^[2].

Signs and symptoms

Many people with myxofibrosarcoma may not have any symptoms at first. Eventually, the most common signs include^[1][2]:

• A painless lump on an arm or leg, usually under the skin
• A lump that grows slowly
• Swelling where the lump is located

The symptoms can vary depending on the size and location of the tumor. Most small myxofibrosarcoma tumors are painless, but large tumors can cause pain or disturbance in the function of nearby organs or tissues^[18].

Causes and risk factors

The cause of myxofibrosarcoma is often not known. Medical experts do not fully understand what causes this cancer to develop^[1][2]. Like all types of cancer, it develops when a change (called a mutation) happens in the cells’ DNA, which holds the instructions that tell cells what to do.

In healthy cells, DNA gives instructions to grow and multiply at a set rate and tells the cells to die at a set time. In cancer cells, the DNA changes give different instructions. The changes tell the cancer cells to grow and multiply quickly. Cancer cells can keep living when healthy cells would die, causing too many cells to accumulate. These cancer cells can form a lump that may grow into healthy body tissue^[1].

More research is needed to understand what causes the mutation in the first place^[2].

Several risk factors have been identified:

• Age: The risk is higher in adults, especially those ages 50 to 70, with myxofibrosarcoma being most common in people aged 60 to 80. It is rare in people under age 30^[2][4][6]
• Gender: The condition affects more males than females, though the difference is slight^[2][6]
• Genetic conditions: Certain inherited conditions that increase sarcoma risk in general, such as Li Fraumeni syndrome and neurofibromatosis Type 1^[2]
• Chemical exposure: Exposure to certain chemicals, like arsenic and herbicides^[2]
• Previous radiation therapy: A history of radiation treatment^[2]

There is no known way to prevent myxofibrosarcoma^[4].

How doctors diagnose this condition

To diagnose myxofibrosarcoma, a healthcare provider will perform a physical exam and ask about symptoms and health history. The provider will check the body for signs of cancer^[1][4]. They may ask if the lump has grown since it was first noticed^[2].

Because myxofibrosarcoma can resemble many other growths and conditions, additional tests are usually needed for an accurate diagnosis^[2]:

Imaging tests create pictures of the inside of the body to help healthcare professionals learn more about the cancer and its size. Common imaging tests include^[1][4][6]:

• MRI (Magnetic Resonance Imaging): This test looks closely at soft tissue, bone, and muscle
• CT scan (Computed Tomography): Used to look for signs that the cancer has spread to other parts of the body
• Ultrasound: Uses sound waves to create pictures of the body
• X-ray: Can help visualize certain structures
• PET scan: May be used in some cases

Biopsy involves taking a sample of tissue for testing. A healthcare provider will remove a small sample of the growth, which goes to a lab where tests can show if cancer is present and what type it is. Sometimes a needle is used to collect the cells (needle biopsy), while other times surgery is needed to get the tissue sample (open biopsy)^[1][2][6].

The diagnosis can be challenging because myxofibrosarcoma looks like other types of cancer and other conditions that are not cancer. There is a lack of well-characterized markers that can easily identify it. Careful imaging and advanced lab tests help the healthcare team make the correct diagnosis^[1][3].

Cancer grading and staging

Myxofibrosarcoma is classified into three grades based on how the cells look under a microscope: low, intermediate, and high grade^[2][3]. The grading is based on the degree of cellularity (how many cells are present), nuclear pleomorphism (how abnormal the cell nuclei look), and proliferative activity (how quickly the cells are dividing)^[3].

High-grade tumors have more abnormal cells than low-grade ones and are more likely to grow and spread fast. Histological grades correlate with distant metastases (when cancer spreads to other parts of the body) and tumor-associated mortality^[2][3].

Cancer staging helps providers understand how advanced the myxofibrosarcoma is and helps them plan treatments. To stage the cancer, providers consider factors like^[2]:

• The tumor’s size
• How much it has grown into surrounding tissues
• Whether it has spread to other parts of the body

Myxofibrosarcoma usually spreads to the lungs first^[2].

Treatment options

Treatment for myxofibrosarcoma typically involves a combination of approaches, with surgery forming the backbone of treatment^[8].

Surgery

The main treatment for myxofibrosarcoma is surgery. The goal is to cut out as much of the cancer as possible^[1][6]. If all the cancer is removed, surgery might be the only treatment needed.

Myxofibrosarcoma can be challenging to treat because it does not form a well-defined tumor. Instead, it often grows into nearby healthy tissue in an infiltrative pattern, which can make it harder to remove completely^[2][3]. To account for this, surgeons remove the tumor along with a small amount (called a “margin”) of surrounding healthy tissue. They check to ensure no cancer cells are hiding out in healthy tissue^[2][6].

If the tumor is in the arms or legs, surgeons perform “limb-sparing surgery” to make sure the limb can continue to work well. In the past, surgeons often had to remove a limb to get rid of all the cancer, but today that is often not needed because of newer treatments^[6][10]. If the cancer has spread, a surgeon may need to perform a partial or full amputation, although this is very rare^[6].

Radiation therapy

Radiation therapy uses powerful energy beams (such as X-rays or protons) to kill cancer cells^[10]. It might be used before surgery to help shrink the myxofibrosarcoma, making it easier to remove. It can also be done after surgery to kill any cancer cells that might be left behind^[1][2][6].

Chemotherapy

Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. It might help control a myxofibrosarcoma that is growing quickly or might be an option if the cancer does not respond to other treatments^[1][10]. Chemotherapy is sometimes used if there is a high risk of the cancer coming back or if the tumor has spread to other parts of the body (metastasis)^[6].

It is not clear how well chemotherapy works for people with myxofibrosarcoma. Some types of chemotherapy have shown to work well while others have not. Patients may be more likely to have surgery (with or without radiotherapy) as their main treatment^[6].

Targeted and experimental therapies

Researchers are learning more about treatments called targeted therapies and immunotherapies. Targeted therapies are drugs that find and attack cancer cells by targeting specific differences that cancer cells have compared to normal cells^[6].

Outlook and recurrence

Myxofibrosarcoma is characterized by a high risk of local recurrence (the cancer coming back in the same area) related to its infiltrative growth pattern^[3]. The cancer often returns after treatment, and when it comes back, it can be more aggressive^[2][10]. Local recurrence occurs in about 23.5% of patients^[19].

Healthcare teams create treatment plans with the goal of removing all cancer cells to make it more likely that the cancer will not come back. After treatment, providers will monitor patients closely and provide additional treatment as needed^[2][10].

The prognosis depends on many factors that healthcare providers will discuss with individual patients. These factors include the tumor’s grade, size, location, and whether it has spread^[2]. Low-grade myxofibrosarcoma tumors show a good prognosis for treatment^[18]. Compared to low-grade myxofibrosarcoma, intermediate- and high-grade tumors have a worse prognosis due to their more aggressive behavior^[3].

Over time, cancer cells can break off from the tumor and travel to other parts of the body, most commonly to the lungs. This is called metastatic cancer^[2].