Undifferentiated sarcoma is a rare form of cancer that originates in the body’s connective tissues, such as muscles, fat, or fibrous tissue. The term “undifferentiated” means these cancer cells appear so abnormal under a microscope that their specific origin cannot be identified, distinguishing them from other sarcomas. Undifferentiated pleomorphic sarcoma (UPS), formerly known as malignant fibrous histiocytoma (MFH), represents a significant portion of adult soft tissue sarcomas, though it remains uncommon overall, affecting fewer than 5,000 people in the U.S. annually.
Symptoms and Common Locations
Symptoms of undifferentiated sarcoma are often non-specific and depend on where the tumor develops within the body. A common initial sign is a growing lump or area of swelling, which may or may not be painful. These masses can appear in various locations, with the arms and legs being frequent sites.
If the tumor grows in a limb, it might cause swelling, numbness, or tingling if it presses on nerves. When undifferentiated sarcoma arises in the abdomen, particularly behind the abdominal organs in the retroperitoneum, symptoms can include pain, a feeling of fullness, constipation, or loss of appetite. Tumors originating in bone may cause localized pain or even pathological fractures.
The Diagnostic Process
Diagnosing undifferentiated sarcoma begins with a thorough review of a patient’s symptoms and a physical examination. Imaging tests are then performed to visualize the tumor’s size, exact location, and its relationship to surrounding structures. Magnetic resonance imaging (MRI) is often used for tumors in the limbs, while computed tomography (CT) scans are common for those in the chest or abdomen. Positron emission tomography (PET) scans may also be employed to help identify areas of increased metabolic activity, which can indicate cancer.
The definitive diagnosis of undifferentiated sarcoma requires a biopsy, where a small tissue sample is collected from the tumor. This sample is then sent to a pathologist, a doctor specializing in analyzing body tissues. Under the microscope, the pathologist examines the cells to determine their characteristics and how aggressive they appear. Specialized tests, such as immunohistochemistry, are performed on the biopsy sample to confirm the undifferentiated nature of the cells, meaning they lack specific markers that would point to another sarcoma subtype.
Staging and Grading
Once diagnosed, undifferentiated sarcoma is staged and graded to determine its advancement and aggressiveness. Staging assesses if the cancer has spread from its original site, often involving chest imaging like a CT scan to check for distant metastases, commonly in the lungs. The American Joint Committee on Cancer (AJCC) TNM system classifies tumors by Tumor (T) size, Node (N) involvement, and Metastasis (M) to distant sites.
Grading, separate from staging, evaluates how abnormal cancer cells appear under a microscope, indicating their potential for rapid growth and spread. Undifferentiated sarcomas are high-grade tumors, often classified as Grade 3, meaning the cells are highly abnormal and tend to grow and spread quickly. Both staging and grading provide information that guides treatment planning.
Treatment Approaches
Treatment for undifferentiated sarcoma often involves a combination of therapies, tailored to the individual patient’s situation, including tumor size, location, and whether it has spread. Surgery is a primary treatment, aiming for complete tumor removal with a margin of healthy surrounding tissue to minimize remaining cancer cells. For tumors in the arms or legs, surgeons strive for limb-sparing operations, though in rare cases, amputation might be necessary if the cancer has extensively spread within the limb.
Radiation therapy is frequently used in conjunction with surgery. It may be administered before surgery (neoadjuvant radiation) to shrink the tumor, potentially making it easier to remove and improving the chances of a complete surgical resection. Alternatively, radiation can be given after surgery (adjuvant radiation) to eliminate any microscopic cancer cells that might have been left behind, thereby lowering the risk of local recurrence.
Chemotherapy, a systemic treatment using drugs to kill cancer cells, is reserved for cases with a high risk of spread or existing metastasis. It can be given before surgery to reduce tumor size or after surgery, especially if the cancer has returned or spread. Targeted therapies and immunotherapies are also explored for advanced or recurrent disease.
Prognosis and Survival Rates
Prognosis for undifferentiated sarcoma varies considerably, influenced by factors like tumor size, location, histological grade, and cancer stage. Successful surgical removal, particularly achieving clear margins, also plays a significant role.
Patient health can influence treatment tolerance and outcomes. While statistics provide a general overview, such as a reported five-year survival rate of around 60% for high-grade undifferentiated pleomorphic sarcoma, these are population-based estimates and do not predict individual outcomes. A patient’s healthcare team is the best source for personalized information and a detailed discussion regarding their specific situation and prognosis.