2-year-old girl, referring to emergency department after a fall.
What do you see?
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– An expansile lytic lesion with ill-defined margins (green arrow) is seen on the diaphysis of fibula.
– Lamellated periosteal reaction (red arrow) suggests an aggressive lesion.
Differential diagnosis of an aggressive lytic lesion in a 2-year-old child includes:
– Ewing’s sarcoma
– Langerhans cell histiocytosis
What should be done next?
An MRI scan
Intramedullary hyperintense lesion with extensive surrounding soft tissue and bone marrow edema on coronal STIR image (a) is seen. The lesion is hypointense on T1 WI (b).
Postcontrast coronal (a) and axial fat-suppressed (b) T1-weighted images show extensive enhancement in the lesion and the surrounding soft tissue
Histopathologic examination revealed Langerhans cell histiocytosis.
Langerhans Cell Histiocytosis (LCH)
– LCH is characterised by idiopathic infiltration and accumulation of abnormal histiocytes within various tissues.
– Bone is the most commonly affected tissue in children, with a predilection for axial bones, and femur is the most commonly affected long bone.
– Radiographic appearance of the lesions depends on the site of involvement and the phase of the disease.
– Skull: Calvarium is more affected than the skull base, typically seen as single or multiple well-defined lytic lesions on radiography; T1 hypointense, T2 hyperintense with significant enhancement on MRI. Temporal bone is the most common affected part of skull base seen as destructive lesions with a soft tissue component.
– Spine: Vertebral bodies are affected with relative sparing of posterior elements. A typical vertebra plana appearance may be encountered with total collapse.
– Long bones: Ill-defined lytic lesions with/without cortical destruction are seen usually located at diaphysis or metaphysis. Periosteal reaction may be present. Extensive bone marrow and soft tissue signal changes on MRI may also be helpful in the diagnosis.