Introduction: Who Should Undergo Diagnostics

Dedifferentiated liposarcoma is typically discovered when a person notices a growing lump or swelling on their body, particularly on the arms, legs, or torso. Because this condition is rare and often develops without early warning signs, knowing when to seek medical attention is important for early detection and treatment.^[1]

You should consider seeking diagnostic evaluation if you notice a lump that continues to grow persistently over time, especially if it appears on your arm, leg, or torso. Unlike common fatty lumps called lipomas, which are harmless and usually stay small, dedifferentiated liposarcoma tends to grow larger and feel firmer to the touch. Most people with this condition are adults over the age of 50, with the median age at diagnosis being 68 years old, and it affects men slightly more often than women.^[1]

When dedifferentiated liposarcoma develops in the arms or legs, it can cause noticeable symptoms such as swelling or numbness in the area around the lump, or weakness in the affected limb. If the tumor forms in the torso, particularly in the back of the abdominal cavity (an area called the retroperitoneum, which is the space behind the organs in your belly), it may cause stomach pain or cramping, or you might notice your abdomen gradually increasing in size.^[1]

Sometimes, dedifferentiated liposarcoma is found accidentally during an investigation of other symptoms or during a routine operation for a different condition. When located in the abdominal cavity, the tumor may grow quite large before causing any symptoms, which is why it’s often discovered incidentally during imaging tests performed for other reasons.^[4]

If you experience any of these symptoms, it’s advisable to start with a visit to your general practitioner. Your GP will examine you and, if necessary, refer you to a specialist doctor who can perform more detailed diagnostic tests. Early diagnosis is critically important because dedifferentiated liposarcoma has a greater chance of coming back after treatment and spreading to other parts of the body compared to other types of liposarcoma.^[1]

Diagnostic Methods

When dedifferentiated liposarcoma is suspected, doctors use a series of diagnostic tests to identify the disease and distinguish it from other conditions. These tests help determine the exact nature of the tumor, its size, location, and whether it has spread to other areas of the body.^[1]

Physical Examination

The diagnostic process typically begins with a thorough physical examination. Your doctor will look at and feel any lump or swelling you’ve noticed. During this examination, the doctor checks for noticeable masses by examining and feeling the affected area. They will assess the size, location, and consistency of the lump, and may ask questions about when you first noticed it and whether it has been growing.^[1][4]

The physical examination is an important first step because it helps the doctor decide which additional tests are needed. For example, a lump in your arm or leg can be examined more easily than one deep inside your abdomen, which might require more sophisticated imaging techniques to visualize properly.

Imaging Tests

After the physical examination, your doctor will typically order imaging tests to take detailed pictures of the inside of your body. These scans help assess the tumor’s size, location, and extent, and can also determine if the tumor has spread to nearby tissues or other parts of the body.^[4]

CT scans (computed tomography scans) and MRI scans (magnetic resonance imaging) are the most commonly used imaging tests for diagnosing dedifferentiated liposarcoma. These scans create detailed cross-sectional images of your body, allowing doctors to see the tumor’s exact location and measure its size. They can also show whether the tumor is pressing on nearby structures like nerves, blood vessels, or organs, which helps explain any symptoms you might be experiencing.^[4]

For tumors in the arms or legs, MRI scans are particularly useful because they provide excellent detail of soft tissues, including muscles, fat, and connective tissue. For tumors in the abdomen or retroperitoneum, CT scans are often preferred because they can show a larger area and are better at visualizing the relationship between the tumor and nearby organs.^[4]

These imaging tests are not only important for diagnosis but also for planning treatment. Surgeons use the images to understand exactly where the tumor is located and how to approach removing it safely while preserving as much healthy tissue as possible.

Biopsy

A biopsy is the most definitive diagnostic test for dedifferentiated liposarcoma. This procedure involves taking a small sample of tissue from the tumor and examining it under a microscope. The biopsy allows doctors to identify the tumor’s characteristics and confirm whether it is indeed dedifferentiated liposarcoma rather than another type of tumor.^[1]

The biopsy is often performed using an image-guided needle biopsy, where a doctor uses a CT scan or ultrasound to guide a needle into the tumor and extract a small tissue sample. This is less invasive than surgical biopsy and can usually be done as an outpatient procedure with local anesthesia.^[4]

When examined under a microscope, dedifferentiated liposarcoma shows a distinctive pattern. The tumor is composed of two types of tissue: one part that resembles well-differentiated liposarcoma (which contains abnormal fat cells) and another part that is a high-grade non-fatty sarcoma. This combination is what defines dedifferentiation, meaning the tumor has progressed from a lower-grade to a higher-grade, more aggressive form.^[2][4]

Laboratory analysis of the biopsy sample also looks for specific genetic abnormalities that are characteristic of dedifferentiated liposarcoma. The most important of these is the amplification (increased number of copies) of genes called MDM2 and CDK4, which are located on chromosome region 12q13-15. Detection of MDM2 amplification serves to distinguish dedifferentiated liposarcoma from other types of undifferentiated sarcomas, making it a crucial diagnostic marker.^[2][7]

The biopsy results not only confirm the diagnosis but also provide information about the tumor’s grade, which indicates how abnormal the cancer cells look and how quickly they are likely to grow and spread. This information helps doctors predict the tumor’s behavior and plan the most appropriate treatment strategy.

Diagnostics for Clinical Trial Qualification

When patients with dedifferentiated liposarcoma are being considered for enrollment in clinical trials, additional diagnostic tests may be required beyond those used for standard diagnosis. These tests help researchers ensure that patients meet specific criteria for participation and allow them to monitor how well experimental treatments are working.^[1]

Clinical trials investigating new treatments for dedifferentiated liposarcoma often require confirmation of the MDM2 gene amplification through specialized laboratory testing. This genetic marker is so characteristic of dedifferentiated liposarcoma that it has become a standard criterion for enrolling patients in trials testing drugs that target this specific abnormality.^[2][7]

Some clinical trials may also require testing for additional genetic features beyond MDM2 and CDK4 amplification. Researchers have recently identified specific gene fusions (when two or more genes join together to form a new gene) called CTDSP1/2-DNM3OS in a subset of dedifferentiated liposarcoma cases. Patients with these particular genetic changes might be candidates for trials testing treatments designed to target these abnormalities.^[2]

Staging scans are typically required for clinical trial enrollment to determine the extent of the disease. These may include chest CT scans to check for spread to the lungs, and abdominal or pelvic scans to evaluate the primary tumor and look for evidence of spread to other areas. The staging information helps researchers group patients with similar disease characteristics and ensures that trial results are meaningful and interpretable.^[1]

Blood tests are another common requirement for clinical trial qualification. These tests assess your overall health and organ function to make sure you are healthy enough to receive experimental treatments. They typically include complete blood counts to check your red blood cells, white blood cells, and platelets, as well as tests of kidney and liver function. Some trials may also require specific biomarker testing in blood samples to monitor treatment response.^[9]

Before starting a clinical trial, patients usually undergo baseline imaging studies that will be repeated at regular intervals during the trial to assess how the tumor responds to treatment. These images are carefully measured using standardized criteria called RECIST (Response Evaluation Criteria in Solid Tumors), which define how much a tumor must shrink to be considered responsive to treatment. However, researchers have noted that RECIST may not adequately capture all positive treatment effects in dedifferentiated liposarcoma, particularly vascular changes within these large heterogeneous tumors.^[9]

If you are interested in participating in a clinical trial, your doctor will discuss which additional diagnostic tests are needed and explain how they will be used to monitor your condition throughout the trial. An ongoing clinical trial is currently investigating how suitable chemotherapy is as a treatment for dedifferentiated liposarcoma, and participants in this trial would need to meet specific diagnostic criteria for enrollment.^[1]

Follow-up Diagnostics After Treatment

After completing treatment for dedifferentiated liposarcoma, you will have regular follow-up appointments for several years. These appointments include diagnostic tests to monitor for any signs of the sarcoma returning, since dedifferentiated liposarcoma has a relatively high rate of local recurrence.^[1]

Your follow-up schedule should be provided by your sarcoma clinical nurse specialist. The usual practice includes a chance to discuss any new symptoms you may be experiencing, followed by a physical examination to look for any signs of recurrence. This examination may include an MRI or ultrasound if required, depending on where your original tumor was located and your individual risk factors.^[1]

Regular imaging surveillance is particularly important for dedifferentiated liposarcoma because recurrence occurs in 40 to 75 percent of cases, and metastasis (spread to other parts of the body) occurs in about 10 to 15 percent of cases. Early detection of recurrence or metastasis through these follow-up diagnostics can allow for prompt treatment, which may improve outcomes.^[1]