Pitfalls in the diagnosis of common benign bone tumours in children

Abstract

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. Teaching points • 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.

Fig. 1

Normal variants commonly misinterpreted as bone tumours: a Asymmetric closure of the ischio-pubic synchondrosis, with a pseudotumoral aspect on the left side (arrow). b Supra-condylar process of the humerus (arrowhead). c, d Cortical desmoid of the distal femoral metaphysis (arrows). e Ultrasound: longitudinal scan of the posterior femoral metaphysis demonstrates the bone irregularity of a cortical desmoid (arrowhead) and the insertion of the medial gastrocnemius head (arrow)

Fig. 2

Frontal (a) and lateral (b) X-rays of the right knee: Non-ossifying fibroma—typical radiological aspect

Fig. 3

Frontal X-rays of the left tibia: Non-ossifying fibroma of the distal tibial metaphysis—evolution after fracture [age 7 (a), age 9 (b), age 11 (c)]

Fig. 4

Non-ossifying fibroma—incidental finding on MRI: The lesion is hyperintense on T2 (a), hypointense on T1 with a fluid-fluid level (arrow; b), and it presents peripheral contrast enhancement (c). Lateral X-ray of the tibia demonstrates the typical NOF aspect (d)

Fig. 5

Pedunculated exostosis: a Frontal X-ray of the left knee demonstrates the typical features of exostosis (arrow); also note the cortical defect on the lateral femoral metaphysis (arrowhead). b Ultrasound measurement of the hypointense cartilage cap (between calipers)

Fig. 6

Exostosis of the distal femoral metaphysis—involution over 3 years [age 12 (a), age 13 (b), age 15 (c)]

Fig. 7

Enchondroma of the proximal phalanx (arrowhead). Note the small points of calcification at the proximal aspect of the lesion, highly suggestive of a cartilaginous matrix

Fig. 8

Ollier disease—multiple enchondromas of the hand

Fig. 9

Enchondroma of the fifth metacarpal (arrow) and enchondroma protuberans (arrowhead) of the proximal phalanx

Fig. 10

Typical chondroblastoma of the distal femoral epiphysis: a Frontal X-ray of the right knee: well-defined round osteolytic lesion of the distal femoral epiphysis (arrow). b Sagittal fat-saturated proton density MRI: the lesion is well defined, mostly hyperintense, surrounded by bone oedema and an inflammatory reaction of the adjoining soft tissues. c CT of the right knee: the cortex is interrupted on the posterior border of the lesion (arrow), but no periosteal reaction is identified

Fig. 11

Chondroblastoma of the proximal tibial epiphysis: Frontal (a) and lateral (b) X-rays of the right knee demonstrate an osteolytic epiphyseal lesion, crossing the open physis and extending into the metaphysis. Sagittal fat-saturated proton density-weighted MRI (c) confirms the lesion and the extension across the physis (arrowhead). Note the presence of fluid-fluid levels (arrow)

Fig. 12

Simple bone cyst of the right femoral neck: Frontal (a) and lateral (b) X-rays of the right femur: well-defined central lytic lesion, with internal septa. Transverse T2-weighted MRI (c): a unique, large fluid-fluid level is identified (arrow)

Fig. 13

Aneurysmal bone cyst of the second cervical vertebra (C2): a Lateral X-ray of the cervical spine: large expansile lytic lesion of the posterior arch C2 (between arrowheads). b CT, axial slice, bone windowing: confirmation of the lesion, with extreme thinning and focal interruption of the bone cortex. c CT, axial slice, soft-tissue windowing: fluid-fluid levels (arrows) are identified inside the cyst

Fig. 14

Transverse T2-weighted MRI: aneurysmal bone cyst of the left pubic branch, with multiple small fluid-fluid levels

Fig. 15

Osteoid osteoma of the antero-lateral tibial shaft: Frontal (a) and lateral (b) X-rays of the left tibia: osteosclerotic thickening of the antero-medial diaphyseal cortex. c Axial CT slice of the tibial shaft identifies a small lucent nidus (arrow) within the intense sclerotic cortical proliferation

Fig. 16

Osteoid osteoma of the left talar neck: Frontal (a) and lateral (b) X-rays of the left ankle: large round sclerotic fragment within an osteolytic cavity (arrows); no surrounding reactive osteosclerosis is identified. c Sagittal T1-weighted MRI: intense bone oedema surrounding the lesion. d Sagittal T2-weighted MRI: an intense inflammatory reaction is identified within the ankle joint. e CT, sagittal reconstruction: confirmation of the large nidus, entirely filled by the sclerotic fragment and with almost no surrounding osteosclerosis