The Importance of Biopsy in Sarcoma Diagnosis

Biopsy is critical, because the tissues that are removed during biopsy allow physicians to make a definite diagnosis. A physical exam, patient history, and imaging studies might suggest that a patient has a certain subtype of sarcoma, but that diagnosis can only be made after a pathologist examines the tumor's cells.

Tissue samples can be obtained through needle aspiration or through open surgical methods. Because many soft tissue sarcomas are easy for physicians to locate and feel, needle biopsy is often all that is necessary. Needle biopsies are frequently performed by radiologists under CT guidance.

Sometimes an incisional biopsy is necessary because it allows for the removal of more tissue. This type of biopsy involves making an incision in the skin and obtaining some pieces of the tumor for evaluation. Excisional biopsy (a biopsy that removes the entire tumor) should be avoided in most cases of suspected sarcomas, with rare exception. Instead, a well-planned resection surgery is preferred after the disease has been diagnosed and staged.

The Need for a Specialist

The decision to remove part of the tumor or the entire tumor at the time of biopsy is extremely critical. The importance of having a sarcoma specialist either perform the actual biopsy or guide the treating surgeon in planning a biopsy can not be overstated.

The biopsy is often the first step to a successful limb-sparing procedure. The location of the biopsy incision and the technical aspects of obtaining tissue can have a major impact on subsequent operations.

"The Importance of Biopsy in a Sarcoma Diagnosis" is based upon an excerpt of an ESUN article by Drs. Gebhardt and Buecker. "The Need for a Specialist" is based upon an excerpt of an ESUN article by Dr. Morris.

The Pathologist's Role in Sarcoma Diagnosis

A pathologist is a physician who uses scientifically-based laboratory methods to diagnose and characterize diseases. It is the pathologist who is ultimately responsible for making a sarcoma diagnosis based on the examination of tumor tissue.

Because the pathologist’s analysis of tissue from a patient’s tumor is absolutely critical in sarcoma treatment, sarcoma pathologists are specially trained in the diagnosis of these rare tumors. Correct identification of the specific sarcoma subtype is important because treatment protocols differ for various subtypes of sarcoma. Historically, sarcomas have been classified based on how they look under the microscope. Today it is also possible for pathologists to use molecular diagnostics to assist in diagnosis.

The pathologist’s report contains the diagnosis (the identification of the particular subtype of sarcoma), as well as information about the size, shape, and appearance of the tumor sample, and information about the completeness of resection for surgical specimens. This report might also come with a molecular pathology report, which indicates the presence or absence of specific genetic mutations.

Pathologists often practice as consultant physicians who develop and apply their knowledge of tissue and laboratory analyses to assist in the diagnosis and treatment of patients. As physicians and scientists, pathologists specializing in sarcoma employ clinical studies, models of disease, and basic science research to advance the understanding and treatment of sarcoma.

Grading and Staging Sarcomas

The pathologist's report provides an important piece of information called the tumor's grade. The grade refers to a tumor’s appearance under the microscope and is an indication of a tumor’s aggressiveness. High grade tumors behave more aggressively - they are more likely to spread or return after treatment than low grade tumors. Low grade tumors are less aggressive and have a lower chance of spreading or recurring. A tumor's grade is not a guarantee of its behavior, but it is one of the factors that doctors consider when making recommendations for treatment.

After the patient undergoes biopsy and a number of imaging studies, the stage of disease can be assigned. The stage indicates how far the sarcoma has progressed. A small cancer that is limited to one location is in an early stage. Disease that is spread throughout the body is in an advanced stage. It is important to understand that disease staging is not a guarantee of tumor behavior. Staging simply helps the treatment team to make the best recommendations for the patient.

Staging Systems Used for Sarcomas

The two staging systems that are most commonly used for sarcomas are the AJCC system and the Surgical Staging System of the Musculoskeletal Tumor Society (MSTS). This AJCC system classifies the tumor based upon histologic grade, tumor size, location as superficial or deep, and the presence or absence of metastatic disease (see Table 1).

Table 1: AJCC Staging System

Stage	Histological Grade	Size	Location  (Relative to fascia)	Systemic / Metastatic  Disease Present
IA	Low	< 5cm	Superficial or Deep	No
IB	Low	≥ 5cm	Superficial	No
IIA	Low	≥ 5cm	Deep	No
IIB	High	< 5cm	Superficial or Deep	No
IIC	High	≥ 5cm	Superficial	No
III	High	≥ 5cm	Deep	No
IV	Any	Any	Any	Yes

The MSTS staging system classifies tumors based upon the histologic grade of the tumor, its local extent and the presence or absence of metastatic disease (see Table 2).

Table 2: MSTS Staging system

Stage	Histological Grade	Local Extent of Disease	Systemic / Metastatic  Disease Present
Ia	Low	Confined	No
Ib	Low	Unconfined	No
Ia	High	Confined	No
Ib	High	Unconfined	No
III	Any	Any	Yes

"Grading and Staging Sarcomas" is based upon an excerpt of an ESUN article by Carol D. Morris, MD, MS. "Staging Systems Used for Sarcomas" is based upon an excerpt of an ESUN article by Michael Weaver, MD and John Abraham, MD.