Undifferentiated pleomorphic sarcoma


Undifferentiated pleomorphic sarcoma (UPS) is a rare form of cancer that primarily originates in the soft tissues of the body. These soft tissues encompass various types, such as blood vessels, fat, fibrous tissues (including tendons, ligaments, and cartilage), muscles, nerves, and skin. Although UPS typically affects soft tissues, it can also manifest in bones, behaving similarly to other more common boneoriginating sarcomas like osteosarcoma. The most common locations for UPS are the arms and legs, while less frequently, it may occur in the retroperitoneum (the area behind the abdominal organs). 

The name undifferentiated pleomorphic sarcomaderives from the appearance of cancer cells when observed under a microscope. “Undifferentiatedrefers to the cells lacking resemblance to the body tissues in which they develop, while pleomorphicindicates that the cells exhibit multiple shapes and sizes. 

Treatment for UPS depends on the cancer’s location, but it typically involves a combination of surgery, radiation, and drug therapies. It’s important to note that UPS was previously known as malignant fibrous histiocytoma. 


The symptoms of undifferentiated pleomorphic sarcoma vary depending on the location of the cancer within the body. While it most commonly develops in the arms and legs, it can potentially occur anywhere. 

Typical signs and symptoms may include: 

  • Development of a growing lump or an area of swelling. 
  • In case the lump grows large, it may lead to pain, tingling, and numbness. 
  • If the sarcoma appears in an arm or leg, there could be swelling in the hand or foot of the affected limb. 
  • When the cancer occurs in the abdomen, symptoms might include pain, loss of appetite, and constipation. 
  • Fever. 
  • Unintentional weight loss.

If you experience any persistent signs or symptoms that cause concern, it is important to schedule an appointment with a doctor. 


The exact cause of undifferentiated pleomorphic sarcoma remains unclear. However, it is understood that the cancer originates from a cell that undergoes changes in its DNA. The DNA in a cell contains instructions that regulate its functions. When these changes occur, the affected cells start to multiply rapidly, leading to the formation of an abnormal mass of cells, referred to as a tumor. These cells have the ability to invade and damage nearby healthy tissues. Over time, the cancerous cells may also detach from the original tumor and spread to other areas of the body through a process called metastasis. Common sites of metastasis for this type of cancer include the lungs and bones.

Risk factors 

Factors that may increase the risk of undifferentiated pleomorphic sarcoma include: 

  • Advanced age: This cancer is more frequently observed in individuals over the age of 50, although it can occur at any age.
  • History of radiation therapy: In rare instances, undifferentiated pleomorphic sarcoma may develop in areas of the body that have previously undergone radiation treatment.