Enchondroma

Epidemiology and Etiology:

• 10s-30s mostly
• 10-25% of benign bone tumours
• Ollier disease and Maffucci syndrome are mostly sporadic

Common sites:

• medullary bone
• hands & feet (50%)
• proximal humerus
• proximal and distal femur
• exceedingly rare in craniofacial bones

Gross features:

• X-ray:
• Well-marginated
• Range from radiolucent to heavily mineralized
• Punctate, flocculent, or ring and arc patterns of calcification
• Thin rim of ossification around the entire lesion (ring sign)
• No cortical destruction or soft tissue invasion
• Solitary usually
• Multiple in Enchondromatosis (Ollier disease, Maffucci syndrome)
• Frequently limited to a single extremity or one side of the body
• Stop growing at puberty
• <3cm most
• multinodular architecture

Histologic features:

• hypocellular with abundant hyaline cartilage matrix
• pale blue on H&E usually (proteoglycans)
• avascular
• Arising within bony trabeculae, with a thin rim of bone around it
• Chondrocytes evenly distributed or arranged in small clusters
• Situated within sharp-edged lacunar spaces
• Cytoplasm finely granular eosinophilic, often vacuolated
• Small, round nuclei
• Condensed chromatin
• may see:
• binucleate
• more than 1 cell per lacuna
• mitoses very low/absent
• areas of ischemic necrosis common
• allow more cellularity and cytologic atypia in small bones of hands and feet than in long bones
• may see:
• myxoid areas with chondrocytes stellate/bipolar, not in lacunae

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

• diploid
• Ollier disease:
• Mutations of PTHR1 gene
• Increased cAMP signalling

Other features:

• benign
• curettage usually cures
• hot on bone scan
• rare recurrence as low grade chondrosarcoma
• Ollier disease:
• Chondrosarcoma by 40y in 25%
• Maffucci syndrome:
• Higher risk of chondrosarcoma

References:

• WHO book 2002