Fibrous cortical defect

Case contributed by Dr Andrei Tsoriev

Diagnosis almost certain

Presentation

Nonspecific knee pain in female amateur dancer

Patient Data

Age: 9 years

Gender: Female

From the case: Fibrous cortical defect

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Coronal bone window

Right tibial cortical bone shows a well-circumscribed lucency without agressive bone destruction or a soft-tissue mass.

Case Discussion

Fibrous cortical defect (FCD) also known as "non-ossifying fibroma (NOF)" is the most frequent bone lesion in children, occurring in up to 30-40% of children.It is most commonly seen in adolescents. No histologic difference exists between non-ossifying fibromas and cortical fibrous defects. Most large lesions are called nonossifying fibromas (NOF) whereas smaller ones are called fibrous cortical defects. Basically, the terms FCD and NOF are almost interchangeable. Most authors believe these to be the same entity.

These lesions are developmental abnormalities rather than tumors. They are usually incidental findings on x-rays. Small ones have no clinical significance, whereas large ones may result in pathological fracture.FCDs may be multiple.

In this case, FCD most likely represents an incidental finding. Biopsy, intervention and surgery in such lesions should be avoided, and follow-up imaging is generally not necessary.