Peak incidence in third decade

Incidental, asymptomatic finding; often discovered during evaluation for shoulder or knee pain

However, can present with pathologic fracture in the small tubular bones of the hands and feet

Metaphyseal or metadiaphyseal, central

Distribution: hands and feet, 40% to 65%; long tubular bones, 25%

Lytic component, if present, is geographic with nonsclerotic borders

Chondroid pattern, i.e., arcs and stippling

Often mixed lytic and sclerotic pattern

Examples of enchondromas with a typical central, metaphyseal/diaphyseal location in the proximal humerus ( left ) and distal femur ( right ).

Note the typical arcs and whorls of mineralization and lack of endosteal scalloping.

Deep scalloping of endosteal cortex is seen more commonly in short tubular bones ( left ).

Enchondromas can present with pathologic fracture in phalanges ( right ). This does not necessarily imply malignant transformation.

Enchondroma is the most common bone tumor of the phalanges.

Bone scans frequently show mild radionuclide uptake that is less than the anterior iliac crest ( left ).

However, the degree of activity can appear deceptively high on coned-down views if comparison to the iliac crest is unavailable ( right ).