Osteochondroma is a benign bone tumor that presents as a cartilage-capped bony projection on the external surface of bones. It is caused by aberrant growth plate development and is associated with mutations in EXT1 and EXT2 genes. Osteochondroma typically presents in childhood as multiple lesions near joints and can cause deformities. Complications include fractures, bursa formation, arthritis and rare malignant transformation into chondrosarcoma. Diagnosis involves radiology and biopsy. Treatment involves surgery to remove painful or deforming lesions. It has an autosomal dominant inheritance pattern and carriers have a 50% risk of passing the condition to offspring.

1. OSTEOCHONDROMA
PONNILAVAN

2. Disease name and synonyms
Hereditary Multiple Exostoses
Multiple Hereditary Exostoses
Diaphyseal aclasis
Multiple Hereditary osteochondromatosis
Multiple cartilaginous exostoses

3. DEFINITION:
Cartilage capped exo phytic
lesion that grows on external
surface of the bone containing a
marrow cavity continuous with
that of parent bone
Exostosis refers to any
outgrowth of a bone from the
cortical surface

5. PREVALENCE :
Prevalence 1:50,000 persons within the general population
Male to female ratio 1.5:1
Approximately 62% of the patients have a positive family history

6. ETIOLOGY:
Aberrant “paired away” or “displaced” growth plate that possibly rotates
and then grows outwards from the parent bone
Abnormal epiphyseal rests separated from the physeal plate during
development may grow to produce the tumour
Periosteal metaplasia and a defective periosteal ring
Osteochondromas made to genes belonging to the EXT family .These
genes are considered to be tumor suppressor gene leads to neoplasia

7. CLINICAL DESCRIPTION:
Increase in size in the first decade of life
Pedunculated or sessile and can vary widely in size
Nearly , 15% of all patients with osteochondromas have multiple lessions
Fascial bones are not affected
Majority are asymptomatic and located in bones that develop from
cartilage, especially the long bones of the extremities ,predominantly
around the knee

9. HME associated deformity
Short ulna + radial bowing (39 – 60%)
Limb length inequality ( 8 – 33%)
Varus /Valgus angulation (2 – 54%)
Ankle deformity(2 – 54%)
Disproportionate short stature (37 – 44%)

10. COMPLICATIONS:
Osseous and cosmetic deformities
Bursa formation
Arthritis(14%)
Impingement on adjacent tendons, nerves, vessels or spinal cord
Abnormal scar formation
Fracture of the stalk of the lession

12. MALIGNANT TRANSFORMATION:
Most important complication malignant transformation of an
osteochondroma
Clinical signs increase in size and pain.
Malignant transformation leads to secondary peripheral chondrosarcoma
in 94% of cases
Suspicion of secondary chondro sarcoma is indicated by growth of the
tumor after puberty , presence of pain or thickness over 1cm of the
cartilaginous cap in adults

13. HISTOPATHOLOGY:
Grossly the specimens have a well defined bony marrow or broad stalk
covered by a cartilage cap at the broader end
The cartilage gap is usually thicker in younger patients
Microscopically the chondrocytes shows a zonification and superficial ones
are more clustered and seen in lacunae
Amorphous calcification with focal necrosis of cartilage is common

14. DIAGNOSTIC METHODS:
When patient suspected to have osteochondroma , full radiological
documentation, histology ,patient and family history have to be carefully
reviewed
Peripheral blood of the patient may be screened for germline mutations in
EXT1 OR EXT 2
The role of 18 Fluoro – deoxyglucose positron emission tomography needs
to be further established

17. DIFFERENTIAL DIAGNOSIS:
Dysplasia Epiphysealis Hemimelica
Developmental disorder with cartilaginous overgrowth of a portion of one
or more extremities and diagnosed before the age of 15 yrs more often
in boys.
Metachondromatosis
Autosomal dominant mode of inheritance .
Occur in hands and feets
Usually point towards the adjacent growth plate

18. TREATMENT:
Osteochondromas are removed when they cause pain, when they give
functional complaints for instance due to compression on nerves or
vessels or for cosmetic reasons
In case of malignancy , en bloc resection of the lesion and its
pseudocapsule with tumor free margins, preferably in a bone tumor
referral centre , should be performed

19. GENETIC COUNSELLING:
Osteochondromas is an autosomal dominant disorder .
Affected individuals have 50 % risk of transmitting the disorder to their
offspring .

20. PROGNOSIS:
Osteochondromas are benign lesions and do not affect life expectancy
The risk of malignant transformation is 1 – 5 %

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