Retroperitoneal cancer is a group of rare tumors that develop in the back area of the abdomen, in a space called the retroperitoneum. These tumors often grow silently and can reach very large sizes before being discovered, making them one of the most challenging cancers to diagnose and treat.

Understanding Retroperitoneal Cancer

The retroperitoneum is the space located between the lining of the abdominal cavity and the back wall of the abdomen. This area contains several important organs and structures, including the kidneys, pancreas, and major blood vessels such as parts of the aorta and the inferior vena cava. When tumors develop in this location, they are called retroperitoneal tumors or retroperitoneal sarcomas.^[1]

Approximately one third of all tumors that arise in the retroperitoneum are sarcomas, which are cancerous growths. The remaining tumors may include lymphomas, other types of cancerous growths, or benign conditions. Sarcomas themselves are quite rare in the general population, and those that occur in the retroperitoneum make up about 15 percent of all soft tissue sarcomas diagnosed.^[1][3]

The two most common types of retroperitoneal cancer are liposarcoma, which begins in fat cells, and leiomyosarcoma, which originates in smooth muscle tissue. Other less common types include solitary fibrous tumor, pleomorphic sarcoma, malignant nerve sheath tumor, synovial sarcoma, and Ewing’s sarcoma.^[2][4]

Liposarcoma has five different subtypes: well differentiated, dedifferentiated, myxoid, round cell, and pleomorphic. Some of these subtypes grow slowly and do not spread to other parts of the body, while others can grow rapidly and aggressively invade nearby organs.^[2]

How Common Is Retroperitoneal Cancer?

Retroperitoneal sarcomas are very rare. In the United States, soft tissue sarcomas overall account for approximately 8,600 new cases each year, which is less than one percent of all newly diagnosed cancers. Among all soft tissue sarcomas, approximately 15 percent arise in the retroperitoneum.^[1]

In the United Kingdom, there are an estimated 250 to 300 new diagnoses of retroperitoneal sarcoma each year out of about 2,000 total soft tissue sarcoma cases expected annually in England and Wales.^[3]

The rarity of these tumors means that many healthcare professionals may see only a few cases throughout their careers. This is why treatment at specialized centers with experience in managing these complex cancers is strongly recommended. The location of the tumor deep within the body and its tendency to grow to large sizes before detection make retroperitoneal sarcomas particularly challenging compared to sarcomas in other locations, such as the arms or legs.^[3]

Who Is at Risk?

Retroperitoneal sarcomas occur equally in women and men. Although the typical age at diagnosis is around fifty years, these cancers can develop at any age, from children to the elderly.^[1]

Liposarcoma is most commonly diagnosed in middle-aged men between the ages of 50 and 65.^[2]

At this time, the exact causes of liposarcoma and leiomyosarcoma remain unclear. Research suggests that liposarcoma forms when a fat cell undergoes a mutation—a change in its genetic material—and begins to multiply rapidly while failing to die when healthy cells would normally do so. Similarly, leiomyosarcoma appears to result from abnormalities in DNA that lead to abnormal genetic changes and the growth of cancerous cells.^[2]

Several inherited genetic conditions have been linked to an increased risk of developing retroperitoneal sarcoma. These include Li-Fraumeni syndrome, familial adenomatous polyposis (also known as FAP or Gardner syndrome), neurofibromatosis type 1 (also called NF1 or von Recklinghausen disease), tuberous sclerosis (Bourneville disease), Werner syndrome (adult progeria), and nevoid basal cell carcinoma syndrome (Gorlin syndrome).^[1][2][5]

Other risk factors that may increase the likelihood of developing sarcoma include prior radiation exposure from previous cancer treatment, damage to the lymphatic system, a family history of cancer, and long-term exposure to certain toxic chemicals such as vinyl chloride, herbicides, arsenic, and dioxin.^[2][10]

Recognizing the Symptoms

One of the major challenges with retroperitoneal cancer is that it often causes no symptoms in its early stages. Because the retroperitoneum has so much space and is deep within the body, tumors can grow quite large before a person becomes aware of them. In many cases, these tumors are discovered incidentally during medical imaging performed for other reasons.^[4][5]

When symptoms do appear, they are usually related to the tumor’s size and its effect on nearby organs. The most common symptom is a noticeable lump or mass in the abdomen. Some patients may feel their abdomen increasing in size or notice their waistline expanding.^[4]

Other symptoms of liposarcoma include abdominal swelling, abdominal pain, constipation (difficulty having bowel movements), feeling full sooner when eating, and blood in the stool.^[2]

Symptoms of leiomyosarcoma can vary depending on the tumor’s location, size, and whether it has spread. Early stages may have no symptoms at all. As the tumor grows, people may experience a noticeable lump or swelling, pain, unexplained weight loss, nausea, and vomiting. Leiomyosarcoma tumors may cause bleeding in the gastrointestinal tract, leading to black, tarry, foul-smelling stools (called melena), abdominal discomfort, or even vomiting of blood (called hematemesis).^[2]

Additional symptoms can include dull pain in the abdomen or lower back, tiredness, early satiety (feeling full after eating only a small amount of food), loss of appetite, hernia, anemia (low red blood cell count), and swelling in the lower extremities.^[1][4][5]

Because these symptoms are often vague and can be mistaken for more common conditions such as digestive problems or even menopause-related changes, many people delay seeking medical attention. Anyone experiencing a combination of these symptoms, especially a growing abdominal mass, should consult a doctor promptly.^[2]

How Is Retroperitoneal Cancer Diagnosed?

Diagnosing retroperitoneal cancer begins with a visit to a healthcare provider who will take a medical history and perform a physical examination. Because these tumors can present a diagnostic challenge, good quality imaging is essential.^[3]

The most useful diagnostic tool for retroperitoneal sarcoma is a computed tomography scan, commonly known as a CT scan. This imaging test uses special X-ray equipment to create detailed pictures of the inside of the body, showing the tumor, its size, its location, and its relationship to nearby organs and blood vessels. A CT scan is also ideal for planning a biopsy if one is needed.^[1][2]

In some cases, magnetic resonance imaging (MRI) may be used, especially in patients who have allergies to the intravenous contrast dye used in CT scans. MRI is particularly helpful when doctors need to assess involvement of the spinal cord, vertebral openings, nerves, or muscles in the back.^[3]

Other imaging tests may include ultrasound and, in some situations, positron emission tomography (PET) scans. A chest CT scan is typically performed to check whether the cancer has spread to the lungs.^[4]

It can be difficult to determine the exact type of sarcoma based on imaging alone. For this reason, obtaining a tissue sample through a biopsy is important before starting treatment. A biopsy involves removing a small piece of the tumor so that a specialist called a pathologist can examine it under a microscope. This helps confirm whether the tumor is cancerous and identifies the specific type and subtype of sarcoma.^[3][4]

The preferred method is an image-guided, percutaneous core needle biopsy. In this procedure, a doctor uses imaging such as ultrasound or CT to guide a hollow needle into the tumor to collect tissue samples. Multiple cores are usually taken to ensure enough material is available for accurate diagnosis. This type of biopsy is performed by inserting the needle through the skin, so it is less invasive than surgery.^[3]

Once a diagnosis is confirmed, additional tests may be done to determine the stage of the cancer. Staging is the process of finding out whether cancer cells have spread to other parts of the body. This information helps doctors understand the extent of the disease and plan the best treatment approach.^[1]

Preventing Retroperitoneal Cancer

Because the exact causes of retroperitoneal sarcoma are not well understood, there are no specific prevention strategies known to reliably reduce the risk of developing this type of cancer. Unlike some cancers that are linked to lifestyle factors such as smoking or diet, retroperitoneal sarcomas appear to occur randomly in most cases.^[2]

For individuals with inherited genetic syndromes that increase the risk of sarcomas, such as Li-Fraumeni syndrome or neurofibromatosis type 1, genetic counseling may be helpful. Genetic counselors can provide information about the condition, discuss the risks, and in some cases recommend monitoring strategies to detect tumors early if they develop.^[1]

People who have been exposed to high doses of radiation during previous cancer treatment should be aware that this exposure may slightly increase their risk of developing a sarcoma later in life. Regular follow-up with healthcare providers and reporting any unusual symptoms can help with early detection.^[2]

Avoiding long-term exposure to certain toxic chemicals, such as vinyl chloride, herbicides, arsenic, and dioxin, may help reduce risk, although the link between these exposures and retroperitoneal sarcoma is not definitively proven.^[2]

Maintaining overall good health through regular exercise, a balanced diet, adequate sleep, and routine medical check-ups is always advisable, even though these measures have not been specifically shown to prevent retroperitoneal sarcomas.^[2]

What Happens in the Body?

To understand how retroperitoneal sarcoma affects the body, it is helpful to know what normally happens in the retroperitoneum. This space contains connective tissues, fat, smooth muscle, nerves, and blood vessels that support and surround the organs. In a healthy person, cells in these tissues grow, divide, and die in a controlled manner.

In retroperitoneal sarcoma, cells in the fat tissue, smooth muscle, or other connective tissues undergo genetic changes that cause them to grow and divide uncontrollably. Instead of dying when they should, these abnormal cells continue to accumulate, forming a tumor. Over time, the tumor grows larger and begins to take up space in the retroperitoneum.^[2]

Because the retroperitoneum is a large space with room for expansion, tumors can grow to very large sizes before they cause symptoms. As the tumor enlarges, it may press on or displace nearby organs such as the kidneys, intestines, pancreas, or bladder. This pressure can cause pain, changes in bowel or urinary function, or a feeling of fullness. In some cases, the tumor may invade or grow into adjacent organs and blood vessels, making treatment more complicated.^[1][2]

The grade of the tumor—which describes how abnormal the cancer cells look under a microscope and how quickly they are likely to grow—plays an important role in predicting the tumor’s behavior. High-grade tumors tend to grow more quickly and are more likely to spread to other parts of the body, while low-grade tumors grow more slowly.^[3]

Retroperitoneal sarcomas can sometimes spread to other areas of the body through the bloodstream or lymphatic system. The lungs are a common site of spread. When cancer spreads from its original location to another part of the body, it is called metastasis.^[1]

Unfortunately, retroperitoneal sarcomas have a high rate of recurrence, meaning they often come back even after complete removal. This is particularly true for dedifferentiated liposarcomas. The risk of recurrence is one reason why ongoing monitoring and follow-up care are so important for patients who have been treated for this type of cancer.^[2]

Surgery for retroperitoneal sarcoma is complex and can last eight hours or more. It often requires the coordinated efforts of multiple surgical teams, including specialists in general surgery, urology, vascular surgery, and other fields, depending on which organs and structures are involved. The physical and mental demands of this type of surgery are significant for both patients and the medical teams caring for them.^[2][5]