Solitary osteochondroma is a bony exostosis projecting from the external surface of a bone; it usually has a hyaline lined cartilagenous cap.The first person to first describe and clearly illustrate it was Sir Astley Cooper,surgeon and anatomist at St.Thomas and Guy\'s, Hospital,London.
When the lesion is in a single bone,it is called solitary osteochondroma;if two or three bones are involved with no family history, it is called multiple osteochondromas;when the tumours are widespread throughout the skeleton ,there is usually a family history and the condition is called hereditary multiple exostosis.
Most common benign skeletal growth or tumour;represents 50% of all benign bone tumours and 10-15% of all primary bone tumours.
Radiologic features of osteochondroma:
Pedunculated type:
Thin elongated stalk.
Metaphyseal.
Blends with cortex and spongiosa.
Projects away from joint (Coat hanger)
Lucent when en face.
Calcified cartilagenous cap(Cauliflower ,spotty)
Sessile type:
Broad based.
Metaphyseal.
Wide,broad metaphysis.
Lucent when en face.
Calcified cartilagenous cap(uncommon)
Features of osteochondroma suggesting malignant transformation:
Clinical:
30 years of age
Pelvis,shoulder.
<1% of solitary osteochondroma ;20% in HME
Increasing pain and mass at site of known osteochondromas.
Chondrosarcoma most common.
Radiologic:
Thick,irregular calcified cap
Bone destruction.
Soft tissue mass.
Altered appearance on sequential studies.