differential

DDx Soft tissue calcification

Hemangioma (commonest)

AV Malformation

Synovial sarcoma

Chondrosarcoma

MO / HO

Eptheloid sarcoma

TB calcified LN

Xray

Calcification

- central pattern

- often increased opacity compared with bone

Ossification

- peripheral pattern

- similar density to bone

FOG MACHINES

Fibrous Dysplasia, Fibrosarcoma

Osteoblastoma/ Osteoid Osteoma / Osteosarcoma

Giant Cell Tumour 

Malignancy / Mets / Myeloma

Primary

- Ewing's, Osteosarcoma, Chondrosarcoma

- Myeloma

Secondary

- Metastasis

- leukaemia, lymphoma

DDx

Baker's Cyst

Popliteal Anerysm

Soft tissue sarcoma

Osteosarcoma / Parosteal OS

Hemangioma / AVM

Note:

Always do xray for calcification

A Bakers cyst / aneurysm can be calcified

Epidemiology

Uncommon

- 4% OS

Females more common 

- similar to GCT

NHx

Less aggressive locally

- less metastasis

- size / location & duration of symptoms don't correlate with outcome

Arise from cortex of bone / periosteum

- parosteal 

- periosteal

- high grade juxtacortical

It was described in 1983 by Dr. Nora, and is sometimes called Nora's disease or Nora's lesion

Definition

Bizarre parosteal osteochondromatous proliferation 

Epidemiology

Rare lesion 

- occurs most commonly in the hands and feet

Adults in their 20's and 30's

Males = Females

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