Soft Tissue Sarcoma: Diagnosis & Staging

There are more than 50 subtypes of soft tissue sarcoma, many of which have unique genetic “fingerprints.” Memorial Sloan-Kettering doctors are expert in characterizing sarcomas molecularly and genetically, making accurate diagnoses more common. Our researchers have pioneered the molecular diagnosis of many sarcoma subtypes and are leading the search for genetic markers that may help determine the aggressiveness of certain tumor types and their potential response to treatment.

Medical History & Physical Examination

Doctors use medical history and physical examination to determine your symptoms and risk factors, as well as to get a picture of your general health and other information about signs of sarcoma.

Imaging Studies

Imaging studies to identify masses are crucial to good clinical management. The imaging techniques used to diagnose soft tissue sarcoma include the following:

• Ultrasound Because sound waves are reflected differently off of tumors than normal tissues, ultrasound can sometimes identify a mass for biopsy.
• CT In CT, x-ray images are taken of the body from different angles, and then assembled by a computer, producing a cross-section picture of the inside of the body. For patients who have already been treated for sarcoma, PET/CT (positron emission tomography and computed tomography) is now often used in combination to monitor for a recurrence. Combination PET/CT can show both the location and the metabolic signal of actively growing cancer cells. If the PET/CT study indicates a recurrence, your doctor may order a separate CT study for precise information about the location of the tumor.
• MRI This technique is similar to a CT scan but employs large magnets and radio waves to produce images. One advantage of MRI over CT scan is MRI’s capability to show blood vessels in greater detail and to picture cross sections from multiple angles.

Biopsy

In a biopsy, the surgeon removes a tissue sample from the tumor so that it can be examined microscopically by a pathologist. In some cases, imaging studies produce clear evidence that surgery is needed immediately. Even in these situations, biopsy is performed on tissue that has been removed in order to confirm that the tumor is a sarcoma and not another type of cancer or a noncancerous growth. Biopsy also enables doctors to determine the type of sarcoma and its grade — a predictor of the risk of metastasis. In the past decade, researchers have identified gene mutations in the biopsies of many soft tissue sarcomas, allowing for accurate diagnoses based on molecular makeup.

• Fine Needle Aspiration Biopsy In fine needle aspiration biopsy, a doctor uses a fine needle and a syringe to remove tiny pieces of the tumor for microscopic examination. This procedure is sometimes used to determine if a suspicious mass is actually a benign tumor or cyst, or attributable to an infection or some other disease. If examination of the cells indicates sarcoma, incisional biopsy or core needle biopsy is usually required to confirm the diagnosis and determine the aggressiveness (grade) of the cancer.
• Core Needle Biopsy In core needle biopsy (also known as Tru-Cut® biopsy), the most common method of biopsy, a surgeon removes a cylindrical tissue sample measuring about 1.5 millimeters across. An outpatient procedure performed under local anesthesia, a core needle biopsy allows patients to go home immediately following the procedure. Memorial Sloan-Kettering doctors have found that core needle biopsy is as effective as incisional biopsy in making a diagnosis of soft tissue sarcoma in the limbs. The procedure is less invasive and less painful for the patient and produces more rapid results than incisional biopsy.
• Incisional Biopsy In an incisional biopsy, a surgeon cuts through the skin to remove part of a tumor, which is then examined microscopically. An incisional biopsy usually involves a brief hospital admission, usually only a day, along with general or local anesthesia. Previously, almost all patients with soft tissue sarcoma in the limbs had to undergo incisional biopsy prior to treatment. Today, less than 10 percent need an incisional biopsy.
• Excisional Biopsy In an excisional biopsy, a surgeon removes all the visible cancerous tissue and some surrounding tissue. Excisional biopsy is only recommended for small tumors (less than 3 centimeters in diameter) on or near the surface of the body.

Staging

Once all of the necessary diagnostic tests have been completed, doctors will use this information to “stage” or determine how aggressive the tumor is and how far it has spread. This information will then be used to design the appropriate treatment strategy. The standard staging system for sarcomas, which is used by Memorial Sloan-Kettering doctors, is the American Joint Committee on Cancer’s TNM system. It is based on several factors:

• Size of the tumor (T)
• Whether or not sarcoma cells have spread to the lymph nodes, which, in sarcoma patients, is very rare (N)
• Whether or not the sarcoma cells have spread, or metastasized, to other parts of the body (M)

An additional factor known as histologic grade, involving the microscopic examination of the sarcoma cells, is used to stage soft tissue sarcomas.

Once staged, the sarcoma will receive a grading using Roman numerals I to IV (with I representing a small tumor that has not spread, and IV representing the most aggressive tumor that has spread). These numbers are combined with the letters A and B, which denote the diameter of the tumor (A for tumors with a diameter of less than 5 centimeters; B for tumors with a diameter greater than 5 centimeters).

Diagnosis: The Next Phase

In the near future, thanks to advances in molecular and genetic technology, pathologists should be able to determine which drugs will be effective against a particular tumor based on its molecular makeup.

Pathologists use genetic analysis to classify sarcomas into two main categories — those with simple genetic alterations and those with abnormal, highly-complex genetic profiles. Classifying each tumor into one of these two groups is critical to making the best treatment decisions possible.