Introduction

The importance of imaging in understanding liposarcoma 

Liposarcomas are a group of rare malignant cancers that arise from fat cells, otherwise known as adipocytes, typically found deep in the body’s soft tissues, such as the thighs or abdominal area. It often develops and grows without showing obvious symptoms, and therefore, early detection is essential for effective treatment.¹

A swift and accurate diagnosis can help determine the type and size of the tumour, as well as an idea of how far it has spread across the body. This is where medical imaging comes into play. Imaging tools such as CT and PET scans are used to visualise internal body structures, including tumours. This is vital in confirming the diagnosis, creating treatment plans and monitoring the progress of the cancer over time.

What is liposarcoma? A closer look 

How liposarcoma develops and its rarity

Sarcomas describe a vast group of tumours that develop from bone and soft tissue. Of these, liposarcomas are the most common, making up approximately 20% of all soft-tissue sarcomas.³ 

These tumours begin when young fat cells undergo abnormal changes, leading to uncontrolled growth. This is often due to genetic mutations that can disrupt the process of normal differentiation in early-stage fat cells. 

Different subtypes of liposarcoma can arise from different types of mutations, which have different modes of disruption, such as by blocking cell maturation, or by resisting apoptosis, a process of “programmed” cell death important for removing damaged cells and maintaining balance within the body. Absence of or an interference with these processes can underlie the development of cancerous growths. 

How many people are affected by liposarcoma?

Liposarcoma has a low incidence rate, affecting approximately 1 in every 100,000 people. However, recent trends indicate that the prevalence of this subtype of cancer is gradually increasing, particularly in people assigned male at birth.² 

What does liposarcoma look like, and which areas of the body can be affected?

Liposarcoma is most likely to occur in the large muscles of the limbs, such as the thighs and the space between the abdominal organs, known as the retroperitoneum. Sometimes, but less commonly, they can form in the arms, buttocks and other soft tissue extremities. 

It typically appears as a large asymptomatic mass, but liposarcomas can vary widely in appearance and behaviour.³ Some types are mostly made up of fatty tissue and can be benign, while others have more solid or fibrous components and grow more aggressively. 

In their early stages, they often form as painless, slowly-developing growths, and so they only start to show symptoms if and when they reach a significant size, as they begin to press on nearby structures.³ 

Important signs to look out for

• A visible lump (new or previously existing, that appears to grow persistently, often also accompanied by swelling or numbness)
• Blood in vomit and/or stool
• Abdominal pain and cramping

Other signs

• Weakness
• Feeling full quickly
• Unexplained weight changes
• Fatigue

Since liposarcomas often grow silently and deep within the body, they may not be detected until they are in the later stages. Understanding where and how they develop is key to early recognition and proper diagnosis, often aided by imaging and further tissue sampling.

Diagnosing liposarcoma: the role of PET and CT scans 

Once a liposarcoma is suspected, medical imaging tools are critical to detecting a potential tumour deep within the body. They work by scanning the interior of the body, helping doctors locate abnormalities precisely, assess their size, shape, and whether or not they have spread.

Of these imaging tools, a combination of CT and PET scans proves particularly useful in diagnosing sarcomas.⁴

CT scans provide detailed images of the tumour’s structure, while PET scans show how active or aggressive the cancer is. Together, they offer a full picture, allowing for the diagnosis to be confirmed. They also determine the stage of the cancer, and the information they provide can guide decisions about treatment options, such as surgery.

CT scans: seeing inside the body

A detailed look at how CT scans identify the structure of liposarcoma tumours.

What is a CT scan?

A CT (computerised tomography) scan is a non-invasive imaging technique that uses multiple low-energy X-ray beams. It can take many scans of the body from different angles. These X-rays are then captured by an array of detectors and processed by a computer to create detailed three-dimensional images of internal body structures. The final image is displayed as a series of thin slices, called tomographs, which allow doctors to examine organs and soft tissues layer by layer. 

In CT images, less dense tissues appear black, while more dense structures like bone appear white. This feature can also help CT scans differentiate between different subtypes of liposarcoma. ⁵

What liposarcoma looks like on a CT scan 

On a CT scan, liposarcoma can appear in several different ways depending on its subtype.

Well-differentiated liposarcomas often look similar to normal fat but may contain thickened internal bands or nodules that raise suspicion. These tumours are usually large, with well-defined or slightly irregular borders.⁶

In contrast, more aggressive types like dedifferentiated liposarcomas or pleomorphic liposarcomas show less fatty tissue and more solid or dense areas, sometimes with calcifications or fluid-filled spaces.⁶

Why CT scans are useful 

CT scans can determine the tumour’s exact location, size, and relationship to surrounding organs or muscles. This information is crucial for planning treatments. 

Positron emission tomography (PET) scans: detecting tumour activity

PET scans use radioactive glucose to highlight active cancer cells.

What is a PET scan? 

A PET scan is a functional 3D imaging technique that shows how tissues and organs are working, rather than just how they look. Before the scan, a small amount of a radioactive tracer, often a form of glucose called FDG, is injected into the bloodstream.

Glucose is used by cells in the body for energy and metabolism and is crucial for general functioning. Since cancer cells are usually more metabolically active, meaning they use more energy than normal cells, they absorb more of this tracer.⁷ As the tracer breaks down, it emits energy, which is detected by the PET scanner. A computer then collects this data and uses it to create detailed “activity maps”, highlighting areas of high activity that appear as bright spots.

They are often combined with CT scans to give both functional and structural information in a single detailed image.⁴

How liposarcoma appears on a PET scan 

On a PET scan, a liposarcoma may show up as a bright or glowing area, depending on how aggressive the tumour is. Less aggressive, or more benign, liposarcomas might show a lower level of activity and thus barely show up, while more aggressive or malignant ones can appear very bright.  Therefore, this information indicates not only the activity, but also the spread of the tumour over time.

Why PET scans matter

PET scans are especially useful for detecting cancers due to their high energy consumption rate, evaluating how aggressive a tumour is, and monitoring how it responds to treatment. They are therefore also useful in predicting patient outcomes, helping people to manage expectations during the course of the disease.⁸

CT vs. PET summary: what patients should know

Side-by-side comparison to explain how each scan contributes differently to diagnosis, comfort level, limitations and risks.

 (Graphic Made by Esha Prabhu)

What are the risks of CT and PET scanning? 

Radiation risks

PET and CT scans are generally safe but involve radiation exposure.

A CT scan uses X-rays, which slightly increase the lifetime risk of cancer, especially with repeated scans. This is because radiation involves high-energy rays penetrating through the body, which can damage chemical bonds in our DNA. This damage can lead to mutations, which impact how the cell grows and divides. If something goes wrong or if this damage remains unrepaired, it can cause uncontrollable growth, leading to added cancer risks.⁹  

PET scans also have radiation risks as they use a small amount of radioactive tracer, which emits radiation as it decays and passes through the body. However, these risks are minimal.¹⁰

Other risks

Some patients may exhibit allergic reactions to the tracers and contrast dyes used in PET and CT scans, respectively; however, this is extremely rare. It is also not recommended for pregnant patients to undergo CT or PET scans unless absolutely necessary, as they are more vulnerable to risks.

Generally, the benefits of accurate diagnosis and treatment planning using CT and PET scans usually outweigh the risks, but it's important to discuss any concerns with a doctor or professional.

Is there a cure for liposarcoma?

While there isn’t yet a cure for liposarcoma, much like other types of cancer, it can be manageable, depending on the tumour’s type, location and aggressiveness.  

Current and future treatments for liposarcoma

Currently, surgery is offered as the main treatment, aiming to remove the tumour from the body. This can be combined with radiation therapy, also known as radiotherapy, to control further growth and reduce the risk of recurrence.¹¹

In some cases, chemotherapy may also be available if the cancer is more aggressive in nature; however, its effectiveness can vary.

Additionally, advances in research open up new avenues for potential future treatments. These may include targeted therapies, immunotherapy, and personalised medicine, based on genetic profiling and tumour behaviour.

Seeing clearly to treat effectively 

In conclusion, CT and PET scans play a vital role in the diagnosis, evaluation, and management of liposarcoma. When combined, they allow doctors to see both the structure and activity of the tumour. This supports the development of more accurate and informed treatment plans, helping to improve patient outcomes.

Summary

• Liposarcoma is a rare cancer of fat cells, often growing silently
• CT scans show the tumour’s size, structure, and location
• PET scans reveal how active or aggressive the tumour is
• Combined, CT and PET offer a full view for better diagnosis and treatment planning
• Treatment usually involves surgery, sometimes with radiotherapy or chemotherapy
• Risks from scan radiation are low and generally outweighed by the benefits