Abstract
ABSTRACT BACKGROUND: Multiple hereditary exostosis (MHE) is a rare autosomal dominant disorder predisposing to the development of multiple osteochondromas. Malignant transformation is an uncommon complication of osteochondromas and is especially rare in the paediatric population. Making a diagnosis of malignant transformation is recognised as a challenge globally METHODS: We obtained informed consent and ethics approval prior to reviewing the hospital file, radiology and pathology of our index patient, as well as conducting a directed literature search RESULTS: An 11-year-old male with MHE presented with new onset pain in the right leg with an associated inability to weight bear. Plain radiographs and magnetic resonance imaging (MRI) showed features consistent with malignant transformation. The child underwent a Malawer 1 resection of the proximal fibula with no complications. The pathology confirmed a grade 1 secondary peripheral chondrosarcoma (CS) arising in an osteochondroma The rate of malignant transformation in MHE is as high as 36.3% in select specialist tertiary centres. Ninety per cent of the resultant malignancies are chondrosarcomas. Malignant transformation before the age of 20 years is exceptional. Plain radiology is routinely used for monitoring of patients with MHE. Other modalities exist to assess for cartilage cap thickness, a much-debated criterion of malignant change. Pathology is essential for confirmation of malignant transformation as well as to exclude high grade lesions. Treatment is wide local excision (WLE) with limb-sparing surgery and long-term follow-up to detect for local recurrences. CONCLUSION: The malignant transformation of osteochondromas occurs more frequently in individuals with MHE and may even arise in the paediatric population. In the presence of suspicious clinical or radiological features, en-bloc surgical resection and histopathological correlation is mandatory to make the diagnosis. We encourage a multidisciplinary team approach with collaboration between the orthopaedic surgeon, radiologist and pathologist Level of evidence: Level 5 Keywords: multiple hereditary exostosis (MHE), chondrosarcoma, osteochondroma, malignant transformation
Highlights
Multiple hereditary exostosis (MHE), known as multiple osteochondromas (MO), is a rare autosomal dominant disorder with a prevalence of approximately 1 in 50 000 in the general population.[1]
The rate of malignant transformation in MHE is as high as 36.3% in select specialist tertiary centres
Plain radiology is routinely used for monitoring of patients with MHE
Summary
Multiple hereditary exostosis (MHE), known as multiple osteochondromas (MO), is a rare autosomal dominant disorder with a prevalence of approximately 1 in 50 000 in the general population.[1] The majority have germline mutations in either the EXT1 or EXT2 tumour suppressor genes, which encode proteins involved in chondrocyte proliferation and differentiation.[2,3]. Osteochondromas are variably sized, benign cartilaginous neoplasms arising from the external, juxtaepiphyseal region of bones which have formed by endochondral ossification. They may be sessile or pedunculated and are composed of an external cartilage cap, underlying cortical bone, and an innermost medullary cavity which merges with that of the bone of origin.[1,4] The most frequently affected sites include the distal femur, proximal tibia and humerus.[1]. Making a diagnosis of malignant transformation is recognised as a challenge globally
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