Tumour & tumour like: Osteoblastoma (OB)

Shares clinical and histological features with OO
Histologically similar to OO, but the nidus is more than 15 mm
Unlike OO, these do not cause severe pain, relieved by aspirin. Instead they cause dull aching pain or may be asymptomatic
Male: 2:1
Most common site - spine
Most common in 2-3 decade

Plain film:
More than 2 cm
Osseous expansion
May have soft-tissue component

largely lytic with osseous matrix

Low-to-int on T1
Int-to-high on T2
Enhance with Gd

Bone scan:
Marked uptake

OB of spine:
All sites equal

OB of rib:
Well defined, geographical, lytic lesion, slight expansion, sharp sclerotic margin

1. Hughes et al. Benign primary tumours of the ribs. Clin rad (2006): 61:314-322
2. Rodallec MH et al. Diagnostic Imaging of Solitary Tumors of the Spine: What to Do and Say. RadioGraphics 2008;28:1019-1041