Common Benign Tumors
Osteoid Osteoma
INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY
• Osteoid osteoma (Figure 58-1) comprises about 11% of all benign bone tumors in children.
• It has a boy-to-girl predominance of about 3:1.
• It is most commonly found in the femur and tibia, but it is also found elsewhere in the skeleton, including the posterior elements of the spine.
SIGNS AND SYMPTOMS
• Constant pain that may be worse at night
— Nonsteroidal anti-inflammatory drugs (NSAIDs) or aspirin usually provide complete or nearly complete pain relief.
— Physical activity does not affect pain.
• Physical examination may reveal a limp or disuse atrophy of the affected extremity.
• Joint examination findings, including range of motion, will be normal.
• Palpation may reveal the site of the lesion if it is located in an area without significant overlying soft tissue, such as the proximal tibia.
• Scoliosis may be observed with spinous process lesions, but it occurs without the traditionally accompanying rotational deformity.
Figure 58-1. Osteoid osteoma of the femoral neck (circled) in a college runner 18 years of age. Patient presented with right-side groin pain.
DIAGNOSTIC CONSIDERATIONS
• Radiographs may be diagnostic, revealing an area of dense, reactive bone surrounding a radiolucent nidus (see Figure 58-1).
• Computed tomography (CT), magnetic resonance imaging (MRI), or bone scan
— May be necessary to identify lesions in the proximal femur or posterior spine
— Useful for identifying early lesions because onset of pain may precede findings on plain radiographs
• Biopsy may be performed to confirm the diagnosis.
DIFFERENTIAL DIAGNOSIS
• Biopsy will differentiate an osteoid osteoma from infection and a malignant bone tumor. Also, patients with an osteoid osteoma are unlikely to have fever, which is common in patients with Brodie abscess and osteomyelitis.
• Histologically, an osteoblastoma appears the same as an osteoid osteoma; differentiation is based on the size of the lesion, with an osteoid osteoma being less than 2 cm.
TREATMENT
• The preferred treatment is symptomatic care with NSAIDs.
• Radiofrequency ablation (RFA) or en block resection is considered for cases not responsive to symptomatic care.
— If RFA is not safe because the lesion is adjacent to neurologic structures, percutaneous coring or drilling is an option.
• Biopsy is performed to confirm the diagnosis prior to RFA or resection.
EXPECTED OUTCOMES/PROGNOSIS
• Spontaneous resolution of an osteoid osteoma lesion may occur 30 to 40 months after onset of symptoms.
• After RFA, the child can resume physical activity as tolerated, without restriction.
• Successful treatment of spinal osteoid osteoma lesions that cause scoliosis can lead to resolution of scoliosis.
WHEN TO REFER
• Refer to a pediatric orthopaedic surgeon for treatment once the lesion is identified.
RESOURCES FOR PHYSICIANS AND FAMILIES
• American Academy of Orthopaedic Surgeons definition of osteoid osteoma (https://orthoinfo.aaos.org/en/diseases–conditions/osteoid-osteoma)
Osteoblastoma
INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY
• Osteoblastoma is a rare benign bone tumor histologically identical to osteoid osteoma.
• It comprises 1% of primary bone tumors and 3.5% of benign bone tumors.
• It has a boy-to-girl predominance of 2 to 3:1.
• Most patients present between 10 and 20 years of age.
SIGNS AND SYMPTOMS
• Pain is the primary symptom.
— NSAIDs and aspirin therapy may provide pain relief, but the relief may not be as dramatic as that of an osteoid osteoma.
• Soft tissue swelling may be present.
• Occasionally, patients may notice a mass.
• Lesions in extremities may cause a limp or disuse atrophy.
• About 50% of osteoblastoma lesions are located in the spine and may cause a decreased range of motion, painful scoliosis, or neurologic signs and symptoms
DIFFERENTIAL DIAGNOSIS
• An osteoblastoma is histologically identical to an osteoid osteoma, but an osteoblastoma is larger (nidus size > 2 cm) and pain from it is not as readily relieved with NSAIDs.
• An aneurysmal bone cyst (ABC) (Figure 58-2) is clinically and radiographically similar to an osteoblastoma, although ABC usually expands the bone more than osteoblastoma; biopsy will differentiate the two conditions. Also, secondary ABCs can be seen in 10% to 40% of osteoblastomas.
Figure 58-2. Aneurysmal bone cyst defined by a radiograph (A) and a magnetic resonance imaging scan (B).
• On radiographs an osteosarcoma is more invasive than an osteoblastoma, causing cortical destruction and significant periosteal reaction; biopsy rules out malignancy.
DIAGNOSTIC CONSIDERATIONS
• Results of laboratory studies are usually normal.
• Findings on plain radiographs are often nonspecific.
— The lesion is usually diaphyseal or metaphyseal and may be cortical or intramedullary.
— Cortical lesions expand the cortex and have a thin rim of reactive bone.
— The lesion has mixed qualities with radiodense and radiolucent areas.
— Typical findings in the spine include enlargement of the spinous process, decreased pedicle definition, and irregular cortex.
• Bone scan or CT scan may be necessary to locate and further evaluate spinous process lesions, which may be difficult to identify on radiographs.
• CT scan may also help to differentiate from malignant lesions, which is sometimes difficult with radiographs.
TREATMENT
• Some smaller lesions may be followed with serial radiographs.
• Lesions are often locally aggressive and require wide surgical resection to prevent damage to surrounding structures. More recently, RFA has been shown to be a safe and effective treatment modality for spinal osteoblastoma.
EXPECTED OUTCOMES/PROGNOSIS
• As with an osteoid osteoma, if spine lesions are identified and treated within 15 months after onset of symptoms, associated scoliosis will resolve or decrease significantly.
• Rarely, sarcomatous degeneration of osteoblastoma lesions has been reported.
WHEN TO REFER
• Refer to a pediatric orthopaedic oncologist once the lesion is identified.
RESOURCES FOR PHYSICIANS AND FAMILIES
• Medscape definition of osteoblastoma (https://emedicine.medscape.com/article/1257927-overview)
Exostosis (Osteochondroma)
INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY
• Exostosis, or osteochondroma, is a common benign lesion, accounting for 10% of all tumors and 30% of all benign bone tumors (Figure 58-3).
Figure 58-3. Sessile exostosis of the distal femur in a boy 10 years of age. This boy presented with a painless mass.
SIGNS AND SYMPTOMS
• Most patients present with a painless mass.
• Some patients may report pain because of repeated trauma to the exostosis or due to bursitis that can develop from repetitive friction of the tense overlying soft tissues.
• Some patients present with a pathologic fracture of the osteochondroma.
• In asymptomatic patients, lesions are identified on radiographs obtained for other reasons.
• Large lesions may limit joint range of motion, cause neural or vascular compression, or irritate overlying muscle.
• Physical examination reveals a non-tender, fixed mass.
• Range of motion of the adjacent joint may be limited.
• If nerve compression is present, isolated peripheral neurologic signs will be noted.
DIFFERENTIAL DIAGNOSIS
• Multiple hereditary exostoses (MHE) is an autosomal-dominant syndrome in which patients have multiple exostoses.
— Lesions may cause growth disturbance, loss of joint motion, and joint deformity.
— Short stature and deformity of the radius and ulna are common.
DIAGNOSTIC CONSIDERATIONS
• The diagnosis can usually be established with radiographs.
— The exostosis may be pedunculated or sessile and is in continuity with the medullary canal of the bone (see Figure 58-3).
• Advanced imaging is usually unnecessary, but if the diagnosis is unclear on a plain radiograph, an MRI or CT scan can help establish the diagnosis.
TREATMENT
• Surgical intervention in the pediatric age group is indicated if the lesion restricts joint mobility, irritates the overlying muscle, or causes pain due to nerve compression, fracture, or repeated trauma.
• Lesions should be radiographically evaluated annually.
EXPECTED OUTCOMES/PROGNOSIS
• Exostoses grow until skeletal maturity.
• Malignant degeneration is rare but should be considered if there has been rapid growth of the exostosis after skeletal maturity and significant increase in pain.
• Pathologic fractures may occur during physical activity.
• Secondary chondrosarcoma is also rare, but patients with MHE are at greater risk than those with a solitary exostosis.
WHEN TO REFER
• Refer to a pediatric orthopaedic surgeon once the lesion is identified.
RESOURCES FOR PHYSICIANS AND FAMILIES
• American Academy of Orthopaedic Surgeons definition of osteochondroma (https://orthoinfo.aaos.org/en/diseases–conditions/osteochondroma)
Enchondroma
INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY
• Enchondroma is a centrally located, metaphyseal, radiolucent, expansile lesion causing thinning of the cortex; such tumors comprise 11% of benign bone tumors (Figure 58-4).
Figure 58-4. Enchondroma of the fifth metacarpal in a boy 8 years of age. It is a centrally located, metaphyseal, lucent, expansile lesion causing thinning of the cortex. This boy presented with a painless mass in the finger.
• This tumor is most commonly found in the phalanges of the hands and feet; other common locations include the proximal humerus and distal femur.
SIGNS AND SYMPTOMS
• May be asymptomatic or may present with pain or a pathologic fracture
• Physical examination may reveal tenderness at the site of the lesion and the affected digit, or the affected extremity may appear swollen.
DIFFERENTIAL DIAGNOSIS
• Chondrosarcoma appears more aggressive on radiograph with cortical destruction; biopsy may be needed to definitively distinguish it from enchondroma.
• Fibrous dysplasia is diaphyseal rather than metaphyseal and, in long bones, has a more ground-glass appearance, while an enchondroma has a more lytic appearance.
• Multiple enchondroma, also called Ollier disease, is less common than a solitary enchondroma and is usually diagnosed in children younger than 10 years.
— Lesions may be bilateral but are usually worse on one side.
— Angular and shortening deformities of the extremities are common and may require surgical intervention.
DIAGNOSTIC CONSIDERATIONS
• Plain radiographs are obtained first and are often diagnostic.
— Enchondromas are usually found in the metaphysis within the medullary canal, but epiphyseal lesions have been reported.
— Lesions are lucent and expansile, and they may cause thinning of the cortex.
— Periosteal reaction is not usually present.
• MRI may be performed to confirm the diagnosis.
— Lesions are well circumscribed and have a high signal intensity on T2-weighted images and an intermediate signal on T1-weighted images.
TREATMENT
• Asymptomatic enchondromas do not require treatment.
• Symptomatic enchondromas and those associated with a fracture should be treated with curettage and bone grafting.
EXPECTED OUTCOMES/PROGNOSIS
• Unlike with solitary enchondroma, patients with multiple enchondromas are at risk for a secondary chondrosarcoma over time, particularly in the shoulder and pelvis.
WHEN TO REFER
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