One of the most important steps in the diagnosis and management of musculoskeletal neoplasms is the biopsy. An appropriately planned and performed biopsy is imperative to minimize morbidity to the patient and guide treatment in a timely and cost-effective manner. Potential hazards related to biopsy have been investigated by members of the Musculoskeletal Tumor Society, and early referral to the appropriate treatment center before obtaining a biopsy helps to avoid errors, complications, and poor outcomes. However, most patients presenting with musculoskeletal neoplasms have bony metastatic disease or myeloma and often cannot be treated at the limited tertiary-care or quaternary-care cancer centers. Logistically, these individuals therefore should be able to receive appropriate care in their communities. This places the decision for when to biopsy and how to biopsy in the hands of general medical oncologists and orthopaedic surgeons. For this reason, all practicing orthopaedic surgeons should be familiar with these principles and techniques for both certification examination purposes and, more importantly, for actual practice. It is important to describe the principles, indications, techniques, and outcomes of the biopsy of musculoskeletal neoplasms on the basis of historical data, practice among surgeons specializing in sarcoma, and recent literature.

Several key principles of the biopsy of musculoskeletal neoplasms, when followed appropriately, can optimize diagnosis and subsequent management. Although some of these principles are based on biology and technology, others have been developed with the goal of avoiding common pitfalls that can affect the diagnosis, definitive management, and outcome. Each of the principles shares a common goal of minimizing morbidity and maximizing diagnostic accuracy, while remaining economically and medicolegally prudent. The key principles are as follows:

When these principles are followed, the correct diagnosis can generally be obtained expeditiously and efficiently with the lowest morbidity for the patient.

Appropriate clinicoradiographic workup should be performed before biopsy.^1,2 An orthopaedic surgeon familiar with musculoskeletal oncology can often perform this workup alone, but the addition of a skilled musculoskeletal radiologist with specific expertise can be invaluable. Although it is much more common for a patient to have a benign rather than a malignant tumor, and a metastatic lesion or myeloma rather than a sarcoma, if the diagnosis of either a bone or soft-tissue sarcoma is considered, referral to a center with a dedicated musculoskeletal oncology team before biopsy should be strongly considered.

Appropriate prebiopsy evaluation is essential for benign lesions as well to avoid unnecessary biopsies. Many lesions can be diagnosed and followed clinically and/or radiographically without a biopsy. Lesions that may not necessitate a biopsy include the following:

An experienced radiologist familiar with musculoskeletal neoplasms may be necessary to assist with determining any of the previously discussed situations.

When evaluating a lesion and planning a biopsy, obtaining appropriate diagnostic imaging is critical. Plain radiography is almost always the initial study of choice when evaluating a bone tumor. It is often the only imaging study necessary to diagnose benign bone lesions such as osteochondromas. Although plain radiography does have some benefit in certain soft-tissue tumors or tumor simulators (eg, synovial sarcoma, heterotopic ossification, or phleboliths in vascular neoplasms), its utility is far less than that in bone tumors.

Bone lesions can be subtle on both plain radiography and CT. MRI is often the advanced imaging modality of choice to follow radiographs in the clinical scenario of bone pain and a possible bone tumor. Subtle lesions on plain radiographs will often become quite evident on MRI (Figure 2). One must keep in mind that the importance of nonaggressive lesions also can be overestimated. Plain radiography and CT are good indicators of bone biology, and the benignancy or malignancy of a bony lesion can often be determined by examining the zone of transition or margination of the lesion. This property cannot be evaluated by using MRI.

With soft-tissue tumors, MRI is the imaging modality of choice. It allows for appropriate localization of viable and necrotic portions of the tumor, definition of the extent of the tumor, and demonstration of diagnostic enhancement patterns, especially when interpreted by radiologists familiar with these lesions. Margination or zone of transition in this situation does not have the
same implications that it does in bone imaging, and these should not be confused.

Other modalities that can aid in diagnosis and planning of the biopsy include ultrasonography, CT, positron emission tomography-CT, and angiography. These modalities are used variably. Although these imaging modalities play different roles in staging, their role in biopsy can be simplified to attaining the most appropriate diagnostic study to confirm clinical suspicion and increase the likelihood of obtaining diagnostic tissue while limiting morbidity.

After it is determined that a biopsy is necessary, the type of biopsy and approach must be planned with foresight toward the definitive surgery and treatment. The goal is to obtain diagnostic tissue with the least amount of contamination of surrounding tissues and morbidity to the patient. Other factors to consider are cost and tissue for research, especially with increasing use of tissue banks and genomic testing. Biopsies can be obtained by percutaneous techniques in the form of core needle biopsy. Although data support open biopsy as the most accurate method of obtaining diagnostic tissue,^4,5,6,7 there are several potential risks associated with this technique; the best current indication for an open biopsy is in the setting of a nondiagnostic core biopsy.⁶ Repeating a core biopsy in the setting of an initially nondiagnostic core biopsy has also been advocated in a study.⁸

The percutaneous biopsy offers minimal morbidity to the patient and can be performed in some office settings⁹ or in the radiology suite using imaging modalities in coordination with or by radiologists. A percutaneous technique for the initial biopsy is widely accepted by sarcoma specialists and increasingly favored over open biopsy in the presence of an experienced team with on-site histologic tissue evaluation and, if necessary, in conjunction with a frozen section to ensure that diagnostic tissue is obtained.¹⁰