Beingn bone tumours

• Bone forming tumours:1. Bone island2. Osteoid osteoma3. Osteoblastoma• Cartilage forming tumour1. Chondroma2. Chondroblastoma3. Chondromyxoid fibroma4. osteochondroma

• Fibrous tumours1. Fibrous cortical defect2. Non ossifying fibroma

Bone island ( aka enostosis)

• Single/multiple• Always medullary in location• Normal compact lamellar bone• Uniformly dense , round/oval lesion• Chr radiating thorn like spicules• Usually <15mm , can be as large as 4cm• Periosteal new bone reaction/ cortical expansion donot occur• Normally bone island donot show increased uptake on bone

scan• In patients with breast- or prostate cancer a bone island can be

mistaken for an osteoblastic metastasis

Osteoid Osteoma

• 20- 30 yrs• M:F=3:1• Intermittent bone pain of several wks/ mnths

duration occuring esp at night with dramatic releif by aspirin

• Diaphysis of long bones are the site of predilection esp at proximal end of femur and tibia

• Spine usually involves neural arch and not the vertebral body

Imaging features

• Round/ oval area of radiolucency with a sclerotic margin

• Radiolucency contains a small dense opacity ( nidus)• Usually prominent periosteal and endosteal reaction.• Radionuclide scan shows intense focal area of

increased activity surrounded by less intense activity from reactive sclerosis

• It must be differentiated from osteoblastoma, and other causes of chronic cortical thickening eg chronic sclerosing osteomyeltis.

Osteoblastoma

• Long h/o pain at night ( relief by aspirin is not a feature)• M=F• <30 yrs• Rare lesion• MC affects spine( esp posterior arch and flat bones • A typical osteoblastoma is larger than 2 cm, otherwise it

completely resembles osteoid osteoma.• There is associated reactive sclerosis• Calcification / ossification of osteoid tissue w/I tumour

may cause amorphous increase in density.

Chondroma

• single tumours are common• MC in phalanges of hand and feet• Although any bone maybe affected• Risk of malignant transformation is greatest in

flat bones.

Imaging features:

• Well defined zone of radiolucency in medulla• Small bones of hand and feet are likely to

expand and thin the overlying cortex• Usually present with incidental fracture • No destruction of cortex occurs• No periosteal reaction occurs• Flecks of calcification are frequenty present

w/I tumour

Juxtacortical chondroma

• arises at the surface of the bone.• Scalloping of cortical bone is possible,• no marrow involvement.• It may be difficult to differentiate from a

periosteal chondrosarcoma.

Multiple enchondromas

Mafucci’s syndrome

• Multiple enchondromas+ cavernous hamenagiomas in soft tissues

Chondroblastoma

• Relatively rare• Epiphysis/apophysis• Long h/o pain• Well defined radiolucent oval lesion within

epiphysis is characterisitic• Thin rim of sclerosis and cortical expansion is seen• Tumour can extend into metaphysis• Stippled calcification occurs in 50% leisons• No malignant transformation

Chondromyxoid fibroma

• 20-30 yrs• M=F• Usually occurs around the knee• Occurs in metaphysis• Radiolucent well defined eccentric

metaphysial lesion with surrounding sclerosis• Cortex maybe expanded• Calcification in lesion is extremely uncommon

Osteochondroma

• Osseous outgrowth from bony cortex• Single>multiple• When multiple k/a diaphyseal aclasia• Very small risk of malignancy (chondrosarcoma)• Arise mainly from tubular bones near metaphysis • MC around knee , proximal end of humerus• Sessile/pedunculated• When pedunculated grows away from metaphysis

being directed towards diaphysis

• Bony protrusions covered by cartilaginous cap• Growth in childhood takes place in the cap,• A thick cartilaginous cap in an adult is

suspicious of chondrosarcoma.

Fibrous cortical defect

• Common lesion• 2-15 yrs• MC around knee ( sp distal posteromedial

femoral cortex)• Blister like expansion of cortex with thin shell

of overlying bone• Always sharply defined, maybe slightly

lobulated

• lucent intracortical defects• outlined by a thin rim of sclerosis• no involvement of the underlying medullary

cavity• no periosteal reaction

Non ossifying fibroma

• Similar to FCD except that it is much larger• 10-20yrs• MC around knee ( esp distal end of femur)• Eccentric well-defined lytic lesion with sclerotic

lobulated margin.• Usually located around the knee in diaphysis or

meta/diaphysis and does not occur in hands, feet, spine and flat bones.

• Found as incidental finding or presents with a fracture.• The natural course is a sclerotic filling over time.