Tumour & tumour like: Enchondroma (EC)

General:
Cartilagenous meduallry tumour

EC of rib:
Second most common benign rb tumour (most common FD)
Most common site - anterior
Lytic lesion, mild expansion, well defined sclerotic margins, punctate calcification, endosteal scalloping
When calcification is not evident, MR is often helpful revealing hyaline cartilage as a lobulated hyperintense foci on T2 and low-to-int on T1

Reference:

1. Hughes et al. Benign primary tumours of the ribs. Clin rad (2006): 61:314-322
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