Sarcomas are rare malignant tumors, representing less than 1% of cancers. There are 50 different types of sarcoma, and they most commonly occur in the extremities. In 15% of cases, sarcomas occur in the retroperitoneum, the "deep" part of the abdomen where the kidneys, pancreas, psoas muscles, and large vessels (aorta and inferior vena cava) are located. The most common sarcoma in the retroperitoneum is liposarcoma. Other types of retroperitoneal sarcomas encountered are leiomyosarcoma, undifferentiated pleomorphic sarcoma, and solitary fibrous tumor.
Retroperitoneal sarcomas present as a mass inside the abdomen. These masses can cause abdominal pain, compress other organs and cause symptoms of nausea and vomiting, urinary problems, changes in bowel habits, or swelling in the legs.
The diagnosis is initially established with an abdominal-pelvic scan, which can identify a mass in the abdomen. An abdominal mass does not always mean a sarcoma diagnosis, several other diagnoses are possible (benign tumors, lymphoma, colorectal cancer, etc.). When a retroperitoneal mass is identified on the scan, the doctor should refer the patient to a sarcoma center where they will be taken care of for biopsy, other necessary investigations and treatment. The definitive diagnosis will be confirmed by a percutaneous biopsy performed in radiology.
Other investigations may sometimes be necessary, including renal scintigraphy (in cases where kidney removal is considered), thoracic scan, complete blood tests, and magnetic resonance imaging. Some sarcomas are more aggressive than others and additional imaging is required to verify the presence of metastases. Sarcomas have the potential to cause distant metastases, the most often affected organ being the lung. Fortunately, when isolated, sarcomas can be treated and ensure a chance of long-term recovery.
Surgery remains the main treatment for sarcomas. During the operation, these masses are often voluminous, and the sarcoma is removed, often including the organs that are attached or included. The organs most frequently removed during surgery are the kidney, psoas muscle, and colon. The small intestine, stomach, pancreas, ovaries, uterus, and certain vessels or nerves may sometimes have to be removed.
Other treatments include radiotherapy and chemotherapy. Radiotherapy can be used before surgery to limit the expansion of the mass. Chemotherapy is reserved for certain subtypes of sarcoma and is used in most cases when the sarcoma is metastatic.
For the optimal treatment of a patient with a sarcoma, they should be transferred to a sarcoma center and taken care of by a dedicated and specialized multidisciplinary team in the treatment of these rare tumors.