Liposarcoma

Liposarcoma is a type of cancer that develops from fat cells. It is classified as a soft tissue sarcoma, which means it arises in the connective tissues of the body. Liposarcomas are most commonly found in areas where fat is normally present, such as the abdomen or limbs. While liposarcoma is rare, it is one of the most common soft tissue sarcoma in adults.

What are the symptoms of liposarcoma?

The symptoms of liposarcoma depend on the size and location of the tumour. Common symptoms include a lump or swelling that may or may not be painful, pressure or discomfort in the affected area, difficulty moving or using a limb if the tumour is near a joint, and symptoms related to organ compression, such as abdominal pain or changes in bowel habits if the tumour is in the abdomen.

What causes liposarcoma?

The exact cause of liposarcoma is not fully understood. However, like other cancers, it develops when genetic changes (mutations) occur in cells, causing them to grow uncontrollably. These changes can happen spontaneously, without a clear cause, or may be influenced by environmental or inherited factors.

What genetic alterations are found in liposarcoma?

Liposarcoma is associated with specific genetic alterations that vary depending on the type of liposarcoma. For example, well differentiated liposarcoma often involves the amplification of the MDM2 and CDK4 genes. Dedifferentiated liposarcoma shares the genetic changes seen in well differentiated liposarcoma but also shows additional alterations associated with a more aggressive behavior. Pleomorphic liposarcoma has complex genetic changes, often involving numerous mutations that reflect its high-grade, aggressive nature.

How is this diagnosis made?

The diagnosis of liposarcoma is made by examining a tissue sample under a microscope, which is typically obtained through a biopsy or surgery. Pathologists look for specific features in the tumour cells that distinguish liposarcoma from other types of tumours. They may also perform additional tests, such as immunohistochemistry or molecular tests, to identify genetic alterations like MDM2 or CDK4 amplification, which can help confirm the diagnosis.

What is the prognosis for a person diagnosed with liposarcoma?

The prognosis for liposarcoma depends on the type of liposarcoma, its location, size, and whether it has spread to other parts of the body. Well differentiated liposarcoma generally has an excellent prognosis and rarely spreads to other body parts, though it can recur if not completely removed. Dedifferentiated liposarcoma has a higher risk of spreading and a worse prognosis compared to the well differentiated type. Pleomorphic liposarcoma is more aggressive and has the highest risk of spread, often leading to a poorer prognosis.

Myxoid liposarcoma has a variable prognosis that depends on its microscopic features. Low-grade myxoid liposarcomas, which consist mainly of a gelatinous (myxoid) background with scattered tumour cells, tend to grow slowly and have a good prognosis. However, cases with round cell morphology, representing a higher grade component, are more aggressive and have a higher risk of spreading to other body parts, including unusual sites like the bones or chest cavity. These higher grade features significantly affect the overall prognosis and treatment approach.

Your doctor will consider the specific type of liposarcoma to determine your treatment plan and prognosis.

What are the types of liposarcoma?

Liposarcoma is not a single disease but a group of cancers with different histologic types. Each type has unique microscopic features, behaviour, and patterns of growth, which influence how it is treated and the expected outcome. The three main types of liposarcoma are well differentiated, dedifferentiated, pleomorphic, and myxoid.

Well-differentiated liposarcoma

Well differentiated liposarcoma usually occurs in middle-aged to older adults. It is most commonly found in the limbs, particularly the thigh or the retroperitoneum, the space behind the abdominal organs. Microscopically, it consists of mature fat cells that closely resemble normal fat but may also include scattered atypical cells with enlarged nuclei. This type is slow-growing and unlikely to spread but can recur locally after surgery.

Dedifferentiated liposarcoma

Dedifferentiated liposarcoma typically occurs in middle-aged to older adults, often in the retroperitoneum or limbs. Microscopically, it shows a combination of well differentiated areas resembling fat and regions of high grade spindle cells, which appear more aggressive. Dedifferentiated liposarcoma is more likely to spread to other parts of the body and requires more aggressive treatment.

Pleomorphic liposarcoma

Pleomorphic liposarcoma is the least common type and usually affects adults but can occur in younger individuals. It is most commonly found in the limbs. Microscopically, it is made up of highly atypical cells with irregular shapes, large nuclei, and areas of necrosis (dead tumour tissue). This type of liposarcoma is highly aggressive and has a high risk of spreading to distant organs.

Myxoid liposarcoma

Myxoid liposarcoma is most often found in younger adults, typically between the ages of 30 and 50. It usually arises in the deep soft tissues of the thigh. Microscopically, it is characterized by a gelatinous (myxoid) background with small, round tumour cells scattered throughout. These cells are often arranged in a delicate network of branching blood vessels. Myxoid liposarcoma can behave differently depending on its cellularity and other microscopic features. Some cases are low grade and grow slowly. In contrast, others may behave more aggressively, particularly if they show areas of round cell morphology, which are higher grade components of the tumour.