Percutaneous musculoskeletal biopsy

Background

Percutaneous, image-guided musculoskeletal biopsy (PMB) is a well-established, safe, and accurate procedure. It has significantly reduced the need for open surgical biopsy—a more invasive and less cost-effective procedure that is associated with a higher complication rate, longer recovery time, and longer time to initiation of therapy. Historically, clinicians have been reluctant to refer their patients for image-guided percutaneous biopsy following reports of diagnostic errors, complications, and unnecessary amputations, particularly if biopsies were performed at centers not specialized in orthopedic oncology. It is now widely accepted that the assessment and biopsy of musculoskeletal lesions should be performed at the institution where the lesion can be definitively managed. Unlike other percutaneous biopsies performed by radiologists, the approach used for biopsy of musculoskeletal lesions, particularly those in the extremities, needs to be closely aligned with the planned surgical approach.

An additional challenge relates to the ever-increasing demand for high-quality tissue samples. Targeted drug therapy for each unique genetic profile is one of the primary goals of a personalized model of patient care. The histologic and biologic heterogeneity of tumors has significant implications for the molecular profiling of cancers, including the ability to identify specific tumor markers and predict the response to targeted therapies. Changes in tumor biology during therapy need to be characterized in patients with disease progression prior to commencing second- and third-line agents. In those with metastatic disease, treatment should be based on the “metastatic” tumor biology, rather than that of the initial diagnostic specimen from the primary lesion. Communication between the interventional radiologist and the orthopedic pathologist is essential to ensure that the appropriate types, quantity, and quality of samples are acquired.

This chapter reviews the approach to percutaneous image-guided biopsy of musculoskeletal lesions. The various techniques and devices are outlined, and the merits, limitations, and complications of each are discussed.

Indications and contraindications

The most common reason to perform musculoskeletal biopsy is to diagnose malignancy or infection ( Table 26-1 ). Solitary bone lesions that are not clearly benign should be regarded as sarcomas until proven otherwise. There are no absolute contraindications to percutaneous biopsy ( Table 26-2 ); however, not all lesions identified by imaging warrant biopsy. A plain-film radiograph or CT of a classic osteoid osteoma does not require biopsy prior to percutaneous ablative therapy ( Figure 26-1 ). Lesions identified incidentally and believed to be latent or active but nonprogressive may be observed, for example, nonossifying fibroma or enchondroma ( Figure 26-2 ). Familiarity with common pseudotumors is essential to avoid unnecessary and possibly hazardous interventions. Lesions that can mimic a tumor include those related to soft tissues and bony structures. Trauma, overuse, infection and symptomatic normal variants are the primary causes of pseudotumors. Many magnetic resonance imaging (MRI)-detected abnormalities and mass-like lesions may have characteristic appearances on plain-film radiography or computed tomography (CT) that enable diagnosis. Examples of pseudotumors include the peripheral calcific rim of myositis ossificans, retained radiopaque foreign bodies, stress fracture of bone, and hydroxyapatite deposition within tendons. In myositis ossificans, biopsy during the early phase of development can give a false-positive diagnosis of osteosarcoma because of the intense osteoblastic activity. The diagnosis may be evident some weeks later when a peripheral rim of calcification might be seen on radiographs or CT imaging. Soft tissue hematomas may be associated with trauma or coagulation disorders, for example, hemophilia or anticoagulant therapy ( Figure 26-3 ). Complex MRI findings can result from repeated hemorrhage into the soft tissues confounded by muscle movement and time elapsed since the bleeding event. A simple hematoma can sometimes be difficult to distinguish from hemorrhage into a tumor. Diabetic myonecrosis is a myopathy associated with poorly controlled diabetes mellitus that may be associated with an intramuscular soft tissue mass ( Figure 26-4 ). Normal variants and their overuse can lead to symptoms and the appearance of a mass on MRI, for example, supernumerary bones, tarsal coalition, and accessory soleus muscle. A ruptured Baker’s cyst may present as a mass in the medial calf on MRI. Extension to the posteromedial knee should enable a diagnosis to be made. Similarly, bursitis tends to occur at reproducible locations around joints and can present as a mass. Metabolic disorders including amyloid deposition and hyperparathyroidism can also be associated with MRI pseudotumors. Brown tumors are a feature of secondary hyperparathyroidism and are frequently nonspecific on MRI ( Figure 26-5 ). The findings may be correlated with hypercalcemia, hypophosphatemia, and high serum parathormone level.

The biopsy of certain lesions needs to be approached with caution ( Figure 26-6 ). Hypervascular masses may be associated with significant morbidity particularly if they are located within a confined space, for example, a limb or the spinal canal. Hemorrhage into a limb compartment may predispose to compartment syndrome. Hemorrhage within the spinal canal may result in cord or nerve root compression. The proximity of vessels and nerves in the neck increases the complication risk for cervical spine biopsy compared with thoracic and lumbar spine biopsies. A safer route for biopsy of lesions involving the odontoid or the dens may be a transpharyngeal approach. Bone biopsy should be avoided whenever possible in the presence of local soft tissue infection.

Patient selection and procedure planning

Preprocedure planning includes a review of the patient’s clinical history, physical examination, and a thorough evaluation of all available imaging studies ( Figure 26-7 ). With a differential diagnosis in mind, the radiologist must determine whether a diagnosis can be made with the information available, confirmed by less invasive means, or that a biopsy is indeed indicated. The technical feasibility of a percutaneous biopsy is determined from a focused clinical examination and review of cross-sectional imaging studies. Planning of the percutaneous biopsy and subsequent surgical resection should then be performed in tandem, particularly if primary malignancy is a consideration and curative surgical intervention a possibility. The local extent of the lesion including proximity to the skin, neurovascular structures, joint capsule, and muscle invasion should be documented. Proximity to scar tissue and graft material from previous surgical procedures should be noted. An approach in which the risk of tumor dissemination is minimized or where the track can be resected with the lesion should be identified. ^, The needle path should be confined to the anatomic compartment involved, avoid neurovascular bundles, and should not cross joint spaces, bursae, tendon, or ligamentous insertions. This is particularly important for limb salvage surgery. Local recurrence rates for sarcomas after open biopsy has been shown to increase from 7% to 38% when the biopsy tract is not excised with the surgical specimen. In patients with Ewing sarcoma, local recurrence is associated with a 5-year overall survival of only 29%. Mankin et al. reported a compromised surgical procedure in 10% and unnecessary amputation in 5% of cases following a poorly planned surgical biopsy. When multiple lesions exist, the biopsy should be taken from the largest and/or most accessible lesion. Maximum yield of viable tissue may be obtained by targeting areas of increased metabolic activity seen on PET CT studies or regions that demonstrate contrast enhancement on CT and MRI scans.

The patient should be informed and educated about the procedure, its benefits, and risks. If pleural transgression is a possibility, for example, paraspinal biopsy, written informed consent should include the possibility of chest-tube placement. A history of anticoagulation therapy and antiplatelet agents should be obtained. Antiplatelet agents should be withheld 5 days before a procedure. Patients receiving low-molecular-weight heparin should have one dose held prior to the procedure. Commonly used laboratory criteria for biopsy include a platelet count greater than 50,000/µL and an internationalized normalized ratio of less than 1.5. Platelet transfusion is recommended for patients with a platelet count less than 50,000/µL. Patient comfort and cooperation may be optimized with the use of conscious sedation, including intravenous midazolam and fentanyl citrate administered by dedicated nursing staff with continuous pulse oximetry and noninvasive blood pressure monitoring. Respiratory compromise, decompensated cardiac failure, morbid obesity and diagnosed sleep apnea, pregnancy, pediatric patient status, and an inability to lie in the required position for the procedure are among the reasons that a referral to anesthesia may be required. Patient cooperation may be required for lesions close to neurologic structures in order to elicit symptoms of nerve impingement—in these cases, local anesthesia alone may be indicated. If infection is a consideration, the radiologic findings should be correlated with the white cell count, C-reactive protein level, and erythrocyte sedimentation rate. Antibiotic therapy, if already started, should be stopped for 24 to 48 hours before biopsy in order to optimize the yield of the microorganism to be sent for culture.

Technique