Biopsies for Sarcoma Diagnosis
Percutaneous Tru-Cut Biopsy
The simplest of biopsies for the patient is the percutaneous or Tru-cut core biopsy. This biopsy is performed in the clinic. In general, your doctor will only feel comfortable performing a biopsy in the clinic if the mass is easily felt on physical exam, is not particularly tender or painful when touched, and is not adjacent to or involving any major blood vessels or nerves.
To perform the biopsy in the clinic, the area of interest is washed carefully with a cleansing solution. The area is numbed using a local anesthetic similar to that used in dental procedures. Once the skin is numb, a small nick is made in the skin. A large core biopsy needle is introduced through the skin and into the area of the tumor. Typically, multiple cores are obtained and sent to the pathology lab for evaluation.
The percutaneous in-clinic biopsy is generally the quickest way to obtain a diagnosis. Results can often be obtained within three to five days. In general, your physician will want you to return to discuss biopsy results and subsequent treatment plans in detail. This can be a good time to bring other family members and friends to have another set of ears in the room.
The percutaneous biopsy is generally very well-tolerated, and less than 10 percent of patients experience significant pain. There are no activity or driving restrictions placed on patients following the biopsy. Following the biopsy, a steri-strip or butterfly strip will be applied to the area, as well as a small compression bandage the patient can remove once at home. Applying ice periodically throughout the evening may minimize swelling.
Studies have demonstrated that percutaneous core biopsies performed in the clinic provide approximately a 95 percent success rate in distinguishing a malignancy from a benign lesion. Occasionally, a biopsy may be non-diagnostic, making an additional biopsy procedure necessary. The specific type of sarcoma may not be able to be determined on a limited percutaneous biopsy. In general, this does not affect the treatment plan.
CT-guided Percutaneous Biopsy
CT (computed tomography) guided percutaneous core biopsies are similar to biopsies performed in the clinic. They are an excellent way to obtain tissue in a more precise manner. CT-guided biopsies are often recommended by your physician for tumors that are not easily felt (palpated) by the surgeon, or for tumors that are in close proximity or adjacent to important nerve and vascular structures. The CT-guided percutaneous biopsy proceeds in a very similar fashion to the percutaneous biopsy performed in the clinic.
At Froedtert & the Medical College of Wisconsin, CT-guided biopsies are performed by an experienced musculoskeletal radiologist. Patients undergo a brief CT scan of the affected area. The radiologist and your surgeon will have previously discussed the appropriate biopsy tract and placement of the needle to obtain the tissue of interest and minimize subsequent issues. The radiologist will use the CT to directly locate where their needles are being placed, after giving the patient a local anesthetic. Typically, sedation is not given for this biopsy, although patients may be encouraged to take pain medication or relaxing medicine prescribed by a doctor prior to the biopsy.
Ultrasound-guided Percutaneous Biopsy
On occasion, musculoskeletal radiologists will recommend an ultrasound-guided biopsy to localize the tumor instead of a CT scan. An ultrasound-guided biopsy proceeds in the same fashion as a CT-guided biopsy.
Open Surgical Biopsies
There are two types of open biopsies – incisional biopsies and excisional biopsies.
For an incisional biopsy, the patient is taken to the operating room and put under anesthesia. This is typically general anesthesia, although occasionally the procedure can be done under regional anesthesia, such as a spinal or a regional anesthetic bloc given the anesthesia team.
An incision is made in the area of the tumor. The surgeon then dissects down to the tumor and takes a small portion of it to send to the pathology lab. The surgeon does not remove the entirety of the mass. Many patients wonder why the entire mass cannot be removed at this time. Sarcomas send out cells into the surrounding area outside of the visible tumor on an imaging study. If the tumor is just “shelled out” of the normal tissue bed, it will have an extremely high risk for coming back locally. This is called a local recurrence.
One of the main goals of sarcoma surgery is to minimize the risk for local recurrence. During the biopsy process, tumor cells are removed through the biopsy tract. Therefore, the biopsy tract or path becomes seeded with tumor cells. The proper way to remove the tumor subsequent to an open incisional biopsy is to remove the biopsy tract in its entirety at the time of the wide surgical resection.
In general, sarcomas benefit from pre-operative radiation therapy and possibly chemotherapy. Leaving the majority of the tumor intact allows the surgeon and the interdisciplinary team to determine the affect of the radiation and chemotherapy on the local tumor. This helps in future planning, should the sarcoma recur locally or spread throughout the body.
An excisional biopsy is a biopsy in which the entire mass or tumor is removed. This is performed for smaller tumors or tumors confined to the subcutaneous tissue between the skin and the deep muscle and fascia. An excisional biopsy generally will involve a marginal excision of the mass. This means there is not a significant amount of normal tissue removed with the tumor. A marginal excision is typically reserved for tumors that appear to be benign or tumors the surgeon thinks are unlikely to be sarcomas.
An excisional biopsy of a sarcoma with a marginal excision will not be adequate to control the local tumor and keep it from recurring. When this occurs, the patient requires further treatment, which might include post-operative radiation therapy to minimize risk for local recurrence and/or a wide re-excision of the previous biopsy tract. The goal of the wide re-excision is to remove the previous biopsy tract and get a cuff of normal tissue around the previous path of the biopsy to minimize the risk for local recurrence.
There may be times when the surgeon elects to do an excisional biopsy with a small cuff or a small amount of normal tissue around the tumor. The goal is to minimize the risk to surrounding tissues and maximize function with the hope that it represents a benign entity. There may be questionable margin status following this procedure, which means the patient may need a further wide excision or further radiation therapy to that area if the mass does turn out to be a sarcoma.
Once the patient has undergone a biopsy, tissue obtained from the tumor is sent to the Pathology Laboratory. At Froedtert & the Medical College of Wisconsin, the tumor is evaluated by a trained musculoskeletal pathologist, who specializes in diagnosing and evaluating bone and soft tissue tumors, including sarcomas. Depending on the amount of tissue obtained and the number of specialized tests the tissue has to undergo, the results of the biopsy may take as little as a couple of days or up to one week. On rare occasions, the tissue will be sent out to other pathologists throughout the country for second opinions, if there is some question with regard to the diagnosis.