- Pictorial Review
- Open Access
Pitfalls in the diagnosis of common benign bone tumours in children
© The Author(s) 2014
- Received: 12 June 2014
- Accepted: 2 September 2014
- Published: 26 September 2014
Benign bone tumours in children are frequent lesions, often with a typical and very identifiable radiological presentation. However, their natural evolution and complications may be the source of variations and errors in interpretation. It is therefore important to understand the possible sources of change in the radiological aspect and to be familiar with common pseudotumoral lesions. The main aim of this review is to review typical aspects of the most common benign bone tumours in children, as well as less frequent variants of these tumours.
• Benign bone tumours in children may have atypical radiological presentations.
• Some normal variants are commonly misinterpreted as tumours.
• X-ray is the main imaging tool for focal bone lesions.
• Depending on the X-ray, complementary imaging examinations and biopsy may be necessary.
- Bone tumour
Benign focal bone lesions are commonly incidental imaging findings in children. Alternatively, they may be the cause of pain, a palpable mass or a pathologic fracture . In all of these instances, the radiologist’s involvement is crucial in the initial description, differential diagnosis and further imaging strategy, if necessary.
Does the lesion have features suggestive of an aggressive nature (Table 2)?
Is further imaging necessary and which technique is best adapted to the residual questions?
Is a biopsy of the lesion required?
Most common “leave me alone” lesions in the paediatric population 
Nonossifying fibroma/cortical defect/cortical desmoid
Solitary bone island (osteoma)
Radiological features of nonaggressive versus aggressive/undetermined bone lesion
Type of lysis
Zone of transition to normal bone
Expansion from slow growth
Aggressive types (sunburst, hair-on-end, linear interrupted, Codman triangle)
Conventional X-ray is still the most important imaging technique for bone lesions, as it demonstrates certain defining aspects, which may be difficult to identify as such by other techniques. Therefore, it should always be part of the imaging algorithm of a focal bone lesion, even if the initial diagnosis was made by a more complex technique, such as CT or MRI.
Whenever a finer, more detailed characterisation of the cortical changes, bone matrix alteration and periosteal reaction is necessary, CT is the adequate technique. It offers a more detailed “radiological” view of the lesion and completes the findings of the X-ray related to bone changes.
MRI is more appropriate to identify the presence of bone oedema as well as identify and quantify infiltration, extraosseous masses and soft tissue changes. As such it is essential in the characterisation of malignant lesions. However, an important caveat must be kept in mind: some very typical radiological lesions, such as nonossifying fibroma, may have nonspecific and sometimes challenging aspects on MRI. Thus, MRI is not adequate as an initial imaging technique, and problematic focal bone lesions incidentally found on MRI require a complementary X-ray.
Even though it lacks specificity, a bone scan is especially useful to demonstrate whether a lesion is uni- or multifocal, an important element in the differential diagnosis. It may also have more specific applications, such as identifying the nidus of an osteoid osteoma in doubtful cases.
Most common locations of benign bone tumours
Most common locations
Location in long bones
Around the knee joint (distal femur/proximal tibia)
Long bones, pelvis, ribs
Around the knee joint (distal femur/proximal tibia), proximal humerus
Simple bone cyst
Proximal humerus, proximal femur
Aneurysmal bone cyst
Long bones, pelvis, posterior elements of vertebrae
Neck of femur, other long bones (especially lower limbs)
Fibrous cortical defect (FCD) and nonossifying fibroma (NOF)
FCD and NOF are both developmental fibro-osseous lesions with similar histological structures. The difference between the two entities is the size, with lesions under 2 cm being considered FCDs and lesions over 2 cm NOFs .
If large, they may take a more “bubbly” aspect and extend toward the medullary bone. Even though they are not expansile lesions, the outer cortex may be thinned or slightly bulged.
NOFs may contain fluid-fluid levels (Fig. 4b), which are by no means specific to any given bone lesion, but merely demonstrate the occurrence of internal bleeding [5, 6]. An X-ray is imperative in order to clarify any doubt in relation to the MRI aspect of an FCD/NOF (Fig. 4d).
A lesion similar to FCD is the cortical desmoid of the distal femoral metaphysis. On a frontal X-ray of the knee, it may be the cause of confusion by appearing as a round, well-defined lucency (Fig. 1c and d). The origin of the lesion is probably repeated microavulsions at the insertion site of the adductor magnus and the medial gastrocnemius head [7, 8].
The diagnosis of a cortical desmoid relies on the typical location and the confirmation of its cortical origin on a lateral X-ray. In doubtful cases, ultrasound is useful to demonstrate the muscular insertion on the cortical defect area and the lack of a tissue mass (Fig. 1e). Even though the same information can be gathered from CT or MRI, these more sophisticated techniques are not necessary .
Considered developmental defects of the growing bone or benign bone tumours of cartilaginous origin, exostoses are the most common benign bone lesion and may take various radiological aspects . Classically they are divided into pedunculated (with a long stalk) and sessile (with a flat base) and their origin is the metaphyseal region of long bones. They may however originate from the pelvic bones or the ribs and take more bizarre, irregular aspects in these regions. Axial skeleton exostoses may be solitary, but they are more common in patients with hereditary osteochondromatosis (multiple exostoses; diaphyseal aclasis).
One normal variant sometimes misinterpreted as an exostosis is the supracondylar process (Fig. 1b). This vestigial bone formation located on the anterior humeral diaphysis has an oblique direction and its tip is oriented toward the distal humeral metaphysis. It is connected to the medial epicondyle by the ligament of Struthers and may rarely be the cause of an entrapment syndrome of the median nerve . Although it is also clearly identified by other imaging techniques, they are rarely necessary, as its location and radiological aspect are so typical. No follow-up or further imaging is required for this entity.
One helpful element is the very intense inflammatory response this tumour causes, which is adequately identified by MRI (Fig. 10b)—in the absence of signs of infection, which orient the diagnosis toward osteomyelitis, this is a helpful sign to distinguish chondroblastoma from other entities [1, 3].
Simple bone cyst
Simple bone cysts are well-defined lucent cystic lesions, centred in the bone, usually located in the proximal humerus or femur. Although termed unicameral bone cysts, these benign lesions do in fact often contain some septa. This is mainly related to the fact that the most common presentation of the cyst is by pathological fracture. Otherwise, they may be incidental findings. The healing process of the fracture induces changes in the simple, unique cystic aspect, with periosteal thickening, septa and contrast enhancement of the cyst lining on MRI. All of these should not be interpreted as signs of aggressiveness.
In time, the physis moves away from the cyst, which becomes diaphyseal. It may also become more sclerotic, with or without treatment.
Aneurysmal bone cyst (ABC)
One of the trickier benign bone tumours is the aneurysmal bone cyst, which is considered more of a post-traumatic accumulation of blood and fluid than a tumoral proliferation in itself. It may be isolated or an associated component of another benign or malignant tumour .
No matter how typical the position and aspect of the lesion, histological confirmation is always necessary, especially to differentiate ABCs from the rare telangiectatic osteosarcoma, which is very similar in macroscopic appearance . Fluid-fluid levels should not be considered more than a suggestive element, as they may appear in an array of benign or malignant lesions, as soon as internal bleeding occurs [5, 6].
Osteoid osteoma is one of the most identifiable benign bone tumours when its clinical and radiological presentations are typical. It is classically a cortical lesion, located in the diaphysis or metaphysis of long bones, the femoral neck being the most common location . However it may be subperiosteal, endosteal or medullary, with most authors considering these locations to result from migration from the typical cortical origin [14, 15].
Although MRI and bone scans are useful to detect an anomaly, the inflammatory changes may sometimes be too diffuse and a small nidus overlooked. The most adequate technique to correctly identify the nidus is CT (Fig. 15c), which is also used subsequently to guide radiofrequency ablation therapy .
The radiological diagnosis of benign bone tumours in children is not always as simple as it may seem. Understanding which events and processes induce variations of the classical imaging presentations and knowing to distinguish normal variants and identify signs of an aggressive process are the key to a correct diagnostic algorithm. It is the radiologist’s responsibility to indicate whether complementary imaging techniques are necessary, which technique is appropriate for the question at hand and whether a biopsy of the lesion is required.
Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
- Kaste SC, Strouse PJ, Fletcher BD, Neel MD (2008) Benign and malignant bone tumors. In: Slovis TL (ed) Caffey’s pediatric diagnostic imaging, 11th edn. Mosby Elsevier, Philadelphia, pp 2912–2969View ArticleGoogle Scholar
- Vanel D, Ruggieri P, Ferrari S, Picci P, Gambarotti M, Staals E et al (2009) The incidental skeletal lesion: ignore or explore? Cancer Imaging 9(A):S38–S43PubMed CentralView ArticlePubMedGoogle Scholar
- Khanna G, Bennett DL (2012) Pediatric bone lesions: beyond the plain radiographic evaluation. Semin Roentgenol 47(1):90–99View ArticlePubMedGoogle Scholar
- Jee WH, Choe BY, Kang HS et al (1998) Nonossifying fibroma: characteristics at MR imaging with pathologic correlation. Radiology 209(1):197–202View ArticlePubMedGoogle Scholar
- Tsai JC, Dalinka MK, Fallon MD, Zlatkin MB, Kressel HY (1990) Fluid-fluid level: a nonspecific finding in tumors of bone and soft tissue. Radiology 175(3):779–782View ArticlePubMedGoogle Scholar
- O’Donnell P, Saifuddin A (2004) The prevalence and diagnostic significance of fluid-fluid levels in focal lesions of bone. Skeletal Radiol 33:330–336View ArticlePubMedGoogle Scholar
- Keats TE, Strouse PJ (2008) Anatomic variants. In: Slovis TL (ed) Caffey’s pediatric diagnostic imaging, 11th edn. Mosby Elsevier, Philadelphia, pp 2556–2593View ArticleGoogle Scholar
- Resnick D, Greenway G (1982) Distal femoral cortical defects, irregularities, and excavations. Radiology 143(2):345–354View ArticlePubMedGoogle Scholar
- An YY, Kim JY, Ahn MI, Kang YK, Choi HJ (2008) Enchondroma protuberans of the hand. AJR Am J Roentgenol 190(1):40–44View ArticlePubMedGoogle Scholar
- Maheshwari AV, Jelinek JS, Song AJ, Nelson KJ, Murphey MD, Henshaw RM (2011) Metaphyseal and diaphyseal chondroblastomas. Skeletal Radiol 40(12):1563–1573View ArticlePubMedGoogle Scholar
- Clapper AT, DeYoung BR (2007) Chondroblastoma of the femoral diaphysis: report of a rare phenomenon and review of literature. Hum Pathol 38(5):803–806View ArticlePubMedGoogle Scholar
- Kransdorf MJ, Sweet DE (1995) Aneurysmal bone cyst: concept, controversy, clinical presentation, and imaging. AJR Am J Roentgenol 164(3):573–580View ArticlePubMedGoogle Scholar
- Sangle NA, Layfield LJ (2012) Telangiectatic osteosarcoma. Arch Pathol Lab Med 136(5):572–576View ArticlePubMedGoogle Scholar
- Laurence N, Epelman M, Markowitz RI, Jaimes C, Jaramillo D, Chauvin NA (2012) Osteoid osteomas: a pain in the night diagnosis. Pediatr Radiol 42(12):1490–1501View ArticlePubMedGoogle Scholar
- Iyer RS, Chapman T, Chew FS (2012) Pediatric bone imaging: diagnostic imaging of osteoid osteoma. AJR Am J Roentgenol 198(5):1039–1052View ArticlePubMedGoogle Scholar
- Szendroi M, Köllo K, Antal I, Lakatos J, Szoke G (2004) Intraarticular osteoid osteoma: clinical features, imaging results, and comparison with extraarticular localization. J Rheumatol 31:957–964PubMedGoogle Scholar