= developmental intracortical bone defect

Age: usually 1^st–2^nd decade; uncommon in boys <2 years of age; uncommon in girls <4 years of age

• asymptomatic

Site: metaphysis of long bone

• well-defined intracortical round / oval lucency
• usually <2 cm long
• sclerotic margins

Cx: pathologic / avulsion fracture following minor trauma (infrequent)

Prognosis:

1. Spontaneous healing resulting in sclerosis / disappearance
2. Ballooning of endosteal surface of cortex = fibrous cortical defect
3. Medullary extension resulting in nonossifying fibroma