Pediatric Orthopedic Tumors
Blaze D. Emerson
Bijan J. Ameri
The most common malignant bone tumor is osteosarcoma (OS) and the Ewing sarcoma family of tumors (ESFT), which account for 90% to 94% of malignant bone tumors.1,2
OSs are the most common primary bone tumor in children with 56% of cases.
It is estimated that 3% of all childhood cancers are OSs, whereas ESFTs are responsible for 34% to 36% of childhood bone cancers.2
Eight types of benign bone tumors have been described: osteoma, osteoid osteoma, osteoblastoma, giant cell tumor, aneurysmal bone cyst, fibrous dysplasia, and enchondroma.
These tumors may be further divided based on the matrix or substance they produce as bone-forming, cartilage-forming, fibrous, and vascular.3
Benign tumors may be static and require no further workup; others may be locally aggressive and require constant supervision and/or treatment.
In most cases, the age of the child, location of lesion, and radiographic appearance are helpful in determining the underlying pathology.4
EPIDEMIOLOGY AND ETIOLOGY
According to the Surveillance Epidemiology, and End Results (SEER) Cancer Statistics Review of the National Cancer Institute program, 3260 new cases of bone and joint cancer will occur in the United States in 2017.
This accounts for approximately 0.2% of all cancers.
Individuals younger than 20 years will account for 26.4% of these cases.
Furthermore, 1550 cancer deaths or 0.3% of all cancer deaths in 2017 will be caused by cancers of the bone or joint.
Overall, the 5-year relative survival is 67.7%.5
Primary bone tumors are relatively uncommon, although malignancy of the bone or joints is the third leading cause of cancer deaths in individuals younger than 20 years.25
It is estimated that 3% to 6% of childhood cancer is attributable to malignant bone tumors.1
The incidence of benign bone tumors is higher than malignant lesions; however, benign tumors are difficult to estimate, as most are found incidentally and patients tend to be asymptomatic.6
Several items in the patient’s history may help guide you toward the diagnosis of a bone tumor.
Variables such as pain, age of patient, location of lesion, and associated symptoms may be useful.
Benign lesions are most often asymptomatic, but patients may present with localized pain, swelling, deformity, or a pathologic fracture.
Aggressive benign bone tumors may cause mild/dull pain that is slowly progressive and worse at night.7
Malignant lesions more commonly present with localized pain of several month’s duration that is rapidly progressive.
Benign bone tumors tend to present during the second decade of life, except for ossifying fibromas, which appear during the first 5 years.
OSs peak between 13 and 16 years and seem to be associated with the adolescent growth spurt.8
During examination, it is important to assess bone tenderness, swelling, deformity, joint range of motion, neurologic function, and vascular function.
Osteochondromas, OSs, ESFT, and periosteal chondromas may sometimes be palpated. Aggressive tumors may compromise neurovascular function.
Overlying erythema or warmth may indicate an underlying infection, which can confuse clinicians.
The best initial modality for suspected primary bone lesions is a plain radiograph.4
It is important to be familiar with the radiographic findings of benign lesions, as 80% to 90% of cases of benign bone tumors may be identified with plain radiographs alone.7
Lack of extension into surrounding tissues
Cortical destruction “moth-eaten”
Spiculated or interrupted periosteal reaction
Extension into the soft tissue
Advanced imaging (computed tomography [CT], magnetic resonance imaging [MRI], scintigraphy) may be needed if the lesions are not clearly benign on plain radiographs.
These modalities may also be needed if the tumors are on the spine, scapula, pelvis, and ribs or if metastasis is suspected (Figure 56.3).7
CT is beneficial for detecting lesions in locations that plain radiographs cannot adequately illustrate.
CT is also useful for more accurately demonstrating the location of the tumor within the bone and changes within the cortex (Figure 56.4).4
MRI is the most sensitive modality for evaluation of medullary changes and defining the extent of the lesion.
MRI provides the best contrast resolution for soft tissue masses and tumor extension into adjacent tissues.
Children with bone tumors should be referred to an orthopedic surgeon who specializes in these lesions.
Most benign tumors may be followed with serial examinations and imaging; however, locally aggressive or malignant lesions may need surgical resection with possible adjuvant therapy.
Specific Malignant Tumors
Primary OS is the most common bony malignancy of children accounting for 56% of cases of malignant bone lesions.2
OS has a worldwide annual incidence rate of 1 to 3 per cases per million and when adjusted for age 4.4 per million cases per year.9
OSs are malignant tumors characterized by the overproduction of osteoid (immature bone).
The tumor is frequently found in the metaphysis of long bones; in decreasing frequency, the femur (75% of cases), proximal tibia, and proximal humerus are the most common locations.2
Most patients have no underlying pathogenesis; however, genetic disposition and exposure to ionizing radiation or chemotherapy are risk factors that have been implicated in the formation of OS.
Secondary OS due to prior chemotherapy or radiation therapy has been postulated to cause up to 3% of new cases.10
The 2 most common genetic predisposition syndromes related to OS are Li-Fraumeni syndrome and retinoblastoma.
OS predominately affects young adults and adolescents, appearing to correlate with the pubertal growth spurt.
Cases of older patients with OS are generally related to prior radiation/chemotherapy exposure or Paget disease.
A genetic predisposition should be assumed when a child younger than 5 years presents with OS.1
Patients may present after an injury and typically complain of chronic localized pain that waxes and wanes over time.
Systemic symptoms are generally absent.
Often, a soft tissue mass is appreciated.
Laboratory evaluation may demonstrate elevations in alkaline phosphatase, ESR, and LDH.
Plain radiographs are the initial imaging modality and demonstrate the characteristic “sunburst pattern,” which is indicative of new bone formation and extension into nearby tissues (Figure 56.7).
The cortex may expand lifting the periosteum and forming what is known as a “Codman triangle” (Figure 56.7).
With rapidly growing tumors, the periosteum cannot produce new bone as fast as the growing lesion, resulting in a pattern of 1 or more concentric shells of new bone over the lesion.