Benign bone tumors are much more common than primary bone malignancies. Orthopaedic surgeons from all disciplines will encounter patients with common benign lesions such as enchondromas, osteochondromas, degenerative cysts, unicameral bone cysts, and nonossifying fibromas. The evaluation of any patient should begin with a detailed history and a physical examination tailored to the history. History should also include the presence of family history of bone tumors, such as in the setting of multiple hereditary exostoses. A thorough pain history must be obtained. Mild pain that is relieved with over-the-counter medication is generally consistent with a benign condition. Pain associated with benign lesions is generally slow in onset and may be related to activity or trauma. Some benign tumors such as osteoid osteoma have a characteristic pain pattern, such as nocturnal pain, that is responsive to NSAIDs. Osteochondromas, particularly in superficial locations such as the medial tibia, may present with pain related to bursitis, mechanical symptoms from impingement on musculotendinous structures, repetitive trauma, or fracture of the base of the tumor. Neurovascular symptoms are rare but can be appreciated in the setting of a large benign bony tumor in an area of anatomic constraint. Lesions in juxta-articular locations must be carefully assessed to rule out other common causes for pain, such as degenerative joint disease or overuse conditions. Most benign lesions do not cause systemic complaints or laboratory abnormalities apart from Langerhans cell histiocytosis, which may be associated with a low-grade fever, rash, or headache and elevated inflammatory markers. Active and aggressive benign lesions may be painful depending on their size and location. Pathologic fractures following a single traumatic event, or after repetitive trauma, may be seen in association with a benign lesion due to compromised bony structural integrity and formation of stress risers (Figure 1). Knowledge of any antecedent pain or symptoms is particularly useful in this scenario and may help guide further workup if a malignant diagnosis is suspected. In addition, there are multiple tumor mimickers that can complicate assessment and should be ruled out when a bone lesion is seen. These mimickers include lesions such as osteomyelitis, bone stress reaction, cortical desmoids, brown tumor, and myositis ossificans.¹ Familiarity with such tumor mimickers and inclusion on a differential diagnosis when indicated (based on history, physical examination, and initial imaging) will ensure adequate workup and management depending on the lesion identified.

If a patient has no pain or symptoms and the lesion is detected incidentally on imaging studies, a benign condition is likely. Variables such as patient age, the location of the lesion within the bone, and plain radiographic characteristics will either confirm the diagnosis as benign or prompt further workup (Tables 1 and 2; Figure 2). Radiographic evaluation should commence with plain radiographs with orthogonal views of the entire bone that contains the lesion. Benign tumors are typically defined by a geographic radiologic margin with a narrow zone of transition and sclerotic border. Endosteal thinning can still be seen with benign tumors (Figure 3), although cortical violation is rarely present. According to a 2022 study, the presence of symptoms, in combination with radiographic findings, may be enough clinical information to help distinguish enchondroma from low-grade chondrosarcoma and decide on nonsurgical or surgical management.²

In general, a thorough history, physical examination, and radiographic assessment should result in a focused differential diagnosis to guide further investigation, including cross-sectional imaging, when indicated. Information regarding matrix formation, endosteal erosion, cortical thinning or violation, and zone of transition are important determinants of a lesion’s biologic potential. In benign-aggressive lesions such as aneurysmal bone cyst or giant cell tumor of bone, cortical destruction may occur and be associated with the formation of a periosteal neocortex. CT provides three-dimensional characterization of the lesion and surrounding bone. CT can also provide information to help the practitioner evaluate the structural integrity of the involved bone or propensity for fracture. CT-based structural rigidity analysis or finite element models can help identify patients at risk for pathologic proximal femur fractures, including use to assess benign conditions such as fibrous dysplasia, bone cysts, and eosinophilic granuloma.^3,4,5 CT can also play a role in the cross-sectional assessment of bone-forming lesions such as osteoid osteoma and myositis ossificans and for areas of complex bony anatomy such as for axial-based and pelvic-based lesions. MRI is helpful in assessing for intraosseous tumor extent with associated marrow edema, soft-tissue extension, pattern of contrast enhancement, and signal characteristics of the lesion. Reactive marrow edema is usually absent or minimal with varying degrees and patterns of contrast enhancement (Figure 4). An exception is with chondroblastoma, which is an epiphyseal benign-aggressive tumor that is well circumscribed with pronounced bony edema on MRI. In benign bone tumors, soft-tissue extension or periosteal reaction is uncommon. Bone scintigraphy or bone scans can be useful as a screening tool to assess for multiple sites of bone involvement, such as in polyostotic fibrous dysplasia, multiple enchondromatosis, or Langerhans cell histiocytosis. Abnormal radiotracer uptake simply indicates a bone response to stimulus and thus does not accurately characterize a lesion as aggressive or malignant. Some benign lesions, such as enchondroma, often show increased radiotracer uptake. Furthermore, a negative or cold bone scan does not exclude a lesion from being aggressive or malignant. Notable examples include purely lytic disease such as multiple myeloma or some types of high-flow metastatic carcinomas such as renal cell carcinoma.