Although upper extremity bone tumors are not commonly diagnosed in the growing child, their presence is often a source of anxiety among families and physicians. Most bone tumors seen in children, however, are benign and the majority can be easily diagnosed based on the history, physical examination, and radiographic characteristics, avoiding mismanagement and unnecessary/inappropriate treatment. In contrast, some benign tumors are more aggressive and may present in a manner similar to sarcomas, therefore is better managed by orthopaedic oncologists at tertiary centers.
The goals of this paper are to highlight the diagnostic approach to bone tumors of upper extremities in the growing child, review the most common tumor types seen in these age group, and provide some important “staying out of trouble” points on the management of these lesions. We limited our detailed discussion to the most common types of benign bone tumors seen in the upper extremities.
After detailed history and physical examination, imaging is an essential step in the approach to these lesions. The history should emphasize several points and key questions such as how was the diagnosis made (presence of mass or symptoms), how long has the mass been present (benign lesions are usually slow growing and have been present for long periods of time), are there any symptoms associated with the tumor (characterization of pain, swelling, neurovascular status), is this an isolated process, is there any family history, or are there other health issues.
The physical examination should not be limited to the upper extremity; it must include the whole musculoskeletal system to rule out associated/multiple lesions. It is important to determine the size, consistence, and mobility of the mass, and the neurovascular status, overall alignment, joint stability, range of motion, and overlying soft tissue structures. Lymph nodes examination is also part of the workup.
Imaging of bone and soft tissue tumors should always start with a plain radiograph. Plain films are not only readily available, easy to obtain, cheap, and do not require sedation or contrast, but also provide the best information about bony lesions in regards to location, size, aggressiveness, structural support, and differential diagnosis. One caveat is that for the plain films to identify bone changes, approximately 30% of the bone has to be involved by the lesion.1–4 Similar to bone sarcomas benign bone tumors also have a tendency to arise near the growth plate of long bones.5
The 5 steps in the radiographic evaluation of a bone lesion are as follows:
- Age: certain lesions have a predilection for certain age groups; for example, bone cysts are commonly seen in the first decade, whereas osteoid osteomas are more frequently seen in the second decade.
- Location: the lesion location within the skeleton and the bone proper, can narrow the differential diagnosis. Although chondroblastoma, Langerhans cell histiocytosis, infection, and giant cell tumor are commonly seen in the epiphysis; fibrous dysplasia, osteoid osteoma, and Ewing sarcoma are more common in the diaphysis. Almost any tumor may be seen in the metaphysis.
- What is the lesion doing to the bone? It is important to evaluate lesional behavior by visualizing the lesional matrix4 (calcification, ground glass, etc.) and the borders2 (wide or narrow zone of transition—helps understanding the rate of growth).
- What is the bone doing to the lesion? This entails the representation of the bone response to the insult, lesions that are being contained are likely slow-growing and benign (usually presents with a halo of sclerosis), whereas lesions that show cortical disruption usually represent an aggressive process that moves faster than the host bone is able to compensate (eg, sarcomas).2
- What is the periosteal reaction? Once a lesion extends beyond the cortex or whenever cortical disruption occurs (eg, pathologic fracture, the periosteal layer attempts to contain the process and at times promote healing). A continuous, solidified periosteal reaction reflects a slow-growing, less aggressive process, whereas a disarranged periosteal reaction (eg, sunburst, onion skin, Codman triangle) represents a fast-growing process that is likely aggressive or malignant.3
Benign bone tumors may be classified according to their activity level6:
- (a) Benign latent: usually asymptomatic lesions, often diagnosed incidentally and sometimes associated with a pathologic fracture (eg, cortical fibrous defect).
- (b) Benign active: represent the majority of benign tumors, tend to grow steadily at a slow rate, may cause symptoms and weaken the bone [eg, unicameral bone cyst (UBC)].
- (c) Benign aggressive: limited number of tumors that present with symptoms, continued growth, pathologic fractures and rarely distant metastasis (eg, chondroblastoma, giant cell tumor).
Biopsy plays an essential role in the diagnosis and management of benign bone tumors; however, it is not done without risks.5,7 The biopsy should be performed after initial workup and formulation of differential diagnosis. Ideally, the treating physician should perform the biopsy. It has been shown that the risk of biopsy-related complications is 5 times higher in the community hospital setting.7 Some of the “rules of biopsy” are described in Table 1. To stay out of trouble, any lesion suspicious for sarcoma or benign but locally aggressive (eg, chondroblastoma, aneurysmal bone cyst (ABC), osteoblastoma, giant cell tumor) should be referred to a tertiary center.
UBC is a fluid-filled cystic lesion that is most commonly seen in the metaphyseal region of the long bones.8 The proximal humerus is one of the most common sites after the distal femur. “Unicameral” suggests a single-chamber cavity without loculations or septae. The cyst lining is composed of fibrous tissue. UBC is usually diagnosed between the ages of 5 and 15 years and approximately 85% of the cases will initially present with a pathologic fracture.9,10
On plain films, UBC is a centrally located, well-defined, slightly expanded, lytic lesion with no periosteal reaction (except in view of a pathologic fracture) or soft tissue mass (Fig. 1). The lesions are considered active if in close proximity with the growth plate, or latent whenever they are located away (>0.5 cm) from the growth plate. Lesion activity seems to be associated with the likelihood of pathologic fracture and recurrence. Pathologic fractures are usually incomplete and characterized by the “fallen leaf” sign (comminuted fragment that floats in the fluid-filled cavity). The fractures usually heal uneventfully in approximately 6 weeks of immobilization.9 Although some tumors heal after the fracture (approximately 10%), the vast majority persists.9,10
Although several different surgical techniques have been described for the treatment of UBC, the recurrence rate is still high (18% to 40%).8,11–14 Methylprednisolone injection into the cystic cavity has been widely used since its original description in 1974 by Scaglietti.15 However, the persistence rate is exceedingly high and multiple repeat injections are invariably needed.11 More recently, several researchers adapted the original aspiration-injection technique and added bone marrow injection,11,14 allograft/bone substitute graft and other grafting materials,12 with improved rate of healing. Based on the etiology theory of venous drainage impairment,16 several researchers have attempted continued cyst decompression to promote healing.13 Based on these different studies, Dormans et al17 devised a minimally invasive technique. Although the healing rate in a long-term follow-up was inferior to the initial results (approximately 95% healing rate), approximately 80% of the cysts healed after the initial procedure and 100% healing was achieved after repeat surgery (unpublished data). In brief, the technique consists of cyst aspiration (confirmation of clear or serous-sanguineous fluid), cystogram (confirmation of single-chamber lesion), open incisional biopsy (frozen section is done on case-by-case basis), curettage (removal of cyst lining), intramedullary decompression (bone marrow grafting), and bone grafting with medical-grade calcium sulfate pellets (scaffolding for new bone formation).17
ABC is a benign but locally aggressive lesion that tends to involve the metaphyseal ends of long bones and the posterior elements of the spine.8 Approximately 50% of the cases occur in the second decade.18 Different than UBC, this lesion presents as a “sponge-like” collection of fibrous tissue and blood-filled spaces, surrounded by a cyst lining. Although the majority of ABCs are primary lesions, often these lesions are seen in association with other benign (eg, chondroblastoma, giant cell tumor) and malignant (eg, telangectatic osteogenic sarcoma) bone lesions.8,19 Most upper extremities lesions present with pain and sometimes swelling. Pathologic fractures may occur (up to 35%). Juxta-articular and juxta-physeal ABCs can cause joint stiffness and growth arrest.20
Radiographically, ABC is an eccentric, expansile (it may expand beyond the adjacent growth plate), lytic, and destructive but well-defined lesion. Periosteal reaction may occur, especially in the case of cortical disruption. Septations are characteristic and may give an appearance of “soap bubbles” (Fig. 2). Magnetic resonance imaging is helpful and demonstrates the septations and fluid-fluid levels (characteristic but not pathognomonic of ABC).21
The treatment of ABCs is surgical. Although fractures may heal, the tumor persists and can continue to grow. Simple curettage and bone grafting have been associated with high recurrence rate (>30%).18,19 Some authors have advocated the use of adjuvants, such as cryotherapy and cementation.22 Complete en bloc resection is limited to large lesions in expandable bones.19 Utilizing a 4-step-approach technique we have obtained excellent results with low recurrence rate (<20%).23 The technique consists of open incisional biopsy and intraoperative frozen section for diagnostic confirmation, followed by tumor resection (4 steps). The tumor is initially curetted; after curettage a high-speed burr is used to improve margins, followed by electro cautery (cyst bed cauterization and inspection) and topical phenol solution 5% (if there is enough distance from the growth plate). After excision, the defect is grafted with a combination of cancellous allograft cubes and demineralized bone matrix paste.23 For the most part, upper extremity lesions do not warrant internal fixation; external bracing is, however, recommended to avoid postoperative pathologic fracture.
FIBROUS CORTICAL DEFECT AND NONOSSIFYING FIBROMA
Fibrous cortical defect (FCD) and non-ossifying fibroma (NOF) are benign latent or active lesions that seem to be related. FCDs are small (1 to 2 cm) and arise within the cortex, usually being diagnosed incidentally. NOFs are the “bigger version” of FCD, they are usually large (>4 cm), can be cortical or intramedullary, and are often diagnosed incidentally but can sometimes be associated with pathologic fractures.10,24 The exact prevalence of these lesions is unknown, but estimates are that FCD may be present in up to 20% of all children.25 In approximately 20% of the cases, multiple lesions are found.25
On plain radiographs, these lesions are eccentric, cortical, or intramedullary-based, well-defined, surrounded by a halo of sclerosis (slow-growing process), uniloculated or multiloculated with a bubbly appearance (Fig. 3).25 A periosteal response is usually absent, unless pathologic fracture has occurred.
Both lesions may regress spontaneously, especially after skeletal maturity.25 Conservative treatment/observation is a reasonable option; however, large lesions, particularly in weight-bearing bones may warrant surgical treatment. The same minimally invasive technique used for UBC17 may be applied to FCD/NOF. In case of large lesions and whenever structural support is wanted, with or without internal fixation, open curettage and bone grafting are also an adequate option.10,24,26
Osteochondromas are a benign cartilaginous exostosis that tends to be asymptomatic unless there are mechanical related symptoms such as impingement to tendons, muscles, or neurovascular structures. Although most cases present as an isolated/single lesion, some children have a multiple hereditary exostosis (MHE) syndrome that is characterized by multiple lesions throughout the skeleton, angular deformities, short stature, sometimes pain, and decreased range of motion and predisposition for malignant degeneration later in life (approximately 20% risk).27 In the upper extremities most osteochondromas are asymptomatic and do not warrant treatment, the exceptions are large lesions and in children with MHE, the angular deformities that are often seen in the forearm.28 In addition, among children with MHE spine lesions may cause neurologic symptoms and cord impingement.
The radiographic appearance of osteochondromas is usually pathognomonic. The lesions arise near the growth plate and can migrate away with skeletal growth. The exostosis shows continuation of the intramedullary bone into the lesion and continuous overlying cortices (Fig. 4). Typically, a large cartilaginous cap is present on the surface of the lesion and it is better seen with magnetic resonance imaging.29
Symptomatic lesions are marginally excised. Inclusion of the cartilage cap and overlying periosteal in the resected specimen is important to reduce the chance of recurrence. Complex reconstructive surgeries are indicated on a case-by-case basis for children with MHE and forearm deformities; although the radiographic results are generally good, it is still questionable whether it has a significant functional impact in the long term.28
Osteoid osteoma (OO) is a rare, benign active, bone-forming tumor that has peak incidence between 10 and 20 years of age. It presents with the classic history of nighttime pain that is readily alleviated with aspirin or nonsteroidal anti-inflammatory drugs.30,31 OO is a small lesion (<2 cm) that may be of difficult visualization on plain films. It presents as a small nidus surrounded by abundant new bone formation extending several centimeters proximal and distal to the nidus. OO may occur anywhere within the bone, including the diaphysis and small carpal bones.30,31 Computed tomography is the gold standard for OO visualization. Bone scan is sometimes helpful to localize the lesion (particularly for spinal OO).
Although curettage is usually successful, it may be very difficult to visualize the nidus intraoperatively (“needle in the haystack”). The “burr down” technique removes the overlying/reactive bone and identifies the cherry-red nidus that should be excised and sent for pathology analysis.32 Recently, computed tomography-guided techniques have been favored, especially for extremity lesions. Radiofrequency or laser ablations have been performed successfully with low recurrence rates.33,34
Enchondroma is the most common benign bone tumor seen in the small tubular bones of the hand, especially in the adult population. Although isolated enchondromas may be seen in the growing child, most of these lesions will present as part of the multiple enchondromatosis complex, or Ollier disease. Children tend to have one side of the body more involved than the other and can present with pain, swelling, fracture, and angular deformities.1
On plain films it presents as a well-defined, intra-medullary lesion that may involve a small area of the bone or its entire width, resulting in cortical thinning, scalloping, and sometimes disruption (Fig. 5). The lesions are usually calcified in a “popcorn” pattern.
Most isolated lesions will be small and not warrant surgical treatment. Sometimes biopsy is needed for diagnostic confirmation. For large (>3 cm) and painful lesions, curettage and bone grafting are recommended. Sometimes severe angular deformity develops and can be addressed with osteotomies.35 Children with Ollier disease have a higher risk of developing malignant degeneration of the primary lesions.36
Several other benign bone tumors may be seen in the upper extremities of growing children; however, due to the succinct nature of this review, we addressed only the most frequently seen. Other bone lesions that may warrant further review include Langerhans cell histiocytosis, chondroblastoma, giant cell tumor, etc.
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