Fibrous cortical defect (historical)

Changed by Yahya Baba, 24 Oct 2022
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Fibrous cortical defects (FCD) are benign bony lesions and histologically identical to non-ossifying fibroma (NOF).

Terminology

The term 'fibrous cortical defect' has been used for bony lesions representing non-ossifying fibromas smaller than 2-3 cm. According to the WHO classification of soft tissue and bone tumours (5th edition) the term is no longer recommended and instead, non-ossifying fibroma (NOF) is preferred 6.

Epidemiology

Fibrous cortical defects typically occur in children (usually 2-15 years), and indeed are one of the most common benign bony lesions, which combined with non-ossifying fibromas are seen in up to 40% of skeletally immature children/adolescents 3. There is a male predilection by a ratio of 2:1 3.

Clinical presentation

They are asymptomatic and self-limiting, completely healing by adulthood.

Pathology

Fibrous cortical defects macroscopically appear as fleshy, fibrous, yellow or tan-brown lesions with variable areas of haemorrhage 3. 

Microscopic examination reveals the lesions to be highly cellular containing spindle-shaped cells on a background of stromal tissue in a prominent storiform pattern. Foamy histiocytes and multinucleated giant cells are also seen. Mitotic figures and/or cellular dysplasia should not be seen 3.

During the healing phase, there is an increase in osteoblastic activity as new bone replaces the defect, gradually being remodelled and completely disappearing 4. 

Radiographic features

Fibrous cortical defectsare benign lytic bone lesions, and, along with fibrous dysplasia share the F in the popular mnemonic FEGNOMASHIC. 

They typically occur in the metaphysis or diametaphyseal junction and appear as small (<2-3 cm) lucent defects within the cortex that over time become sclerotic as they heal. They are typically located in the distal femur or proximal or distal tibia. They are much less frequently seen in the upper limb 3,4.

Importantly, there is no associated soft tissue mass 3.

Plain radiograph and CT

  • lucent intracortical defects

  • outlined by a thin rim of sclerosis

  • no involvement of the underlying medullary cavity

  • no periosteal reaction

MRI

Signal characteristics include:

  • T1: hypointense

  • T2: variable, depending on the phase of healing 3

Nuclear medicine (bone scan)

The appearance depends on the phase of the lesion. In general, they are negative; however, mild hyperaemia and moderate bone uptake are present during healing. If extensive uptake or hyperaemia is present, then an alternative diagnosis or superimposed fracture should be considered 3.

Treatment and prognosis

As these lesions are benign, characteristic in appearance and self-limiting, no treatment, biopsy or even follow-up is required in typical cases. If associated with pathological fracture (more common in non-ossifying fibromas) then cast immobilisation until the fracture has healed, followed by biopsy with or without curettage, and bone grafting may be necessary 3.

History and etymology

The fibrous cortical defect was first described by Dallas Burton Phemister (1882-1951) 5, an American orthopaedic surgeon in 1929 6.

Differential diagnosis

Possible differential considerations include

  • -<li>lucent intracortical defects</li>
  • -<li>outlined by a thin rim of sclerosis</li>
  • -<li>no involvement of the underlying medullary cavity</li>
  • -<li>no <a href="/articles/periosteal-reaction">periosteal reaction</a>
  • -</li>
  • +<li><p>lucent intracortical defects</p></li>
  • +<li><p>outlined by a thin rim of sclerosis</p></li>
  • +<li><p>no involvement of the underlying medullary cavity</p></li>
  • +<li><p>no <a href="/articles/periosteal-reaction">periosteal reaction</a></p></li>
  • -<li>
  • -<strong>T1:</strong> hypointense</li>
  • -<li>
  • -<strong>T2:</strong> variable, depending on the phase of healing <sup>3</sup>
  • -</li>
  • +<li><p><strong>T1:</strong> hypointense</p></li>
  • +<li><p><strong>T2:</strong> variable, depending on the phase of healing <sup>3</sup></p></li>
  • -<li>
  • -<a href="/articles/cortical-desmoid">cortical desmoid</a>: posteromedial aspect of the distal femur</li>
  • -<li>
  • -<a href="/articles/osteoid-osteoma">osteoid osteoma</a>: night pains</li>
  • -<li><a href="/articles/osteomyelitis">osteomyelitis</a></li>
  • -<li><a href="/articles/stress-fracture">stress fracture</a></li>
  • -<li><a href="/articles/intracortical-osteosarcoma">intracortical osteosarcoma</a></li>
  • +<li><p><a href="/articles/cortical-desmoid">cortical desmoid</a>: posteromedial aspect of the distal femur</p></li>
  • +<li><p><a href="/articles/osteoid-osteoma">osteoid osteoma</a>: night pains</p></li>
  • +<li><p><a href="/articles/osteomyelitis">osteomyelitis</a></p></li>
  • +<li><p><a href="/articles/stress-fracture">stress fracture</a></p></li>
  • +<li><p><a href="/articles/intracortical-osteosarcoma">intracortical osteosarcoma</a></p></li>
Images Changes:

Image 14 X-ray (Lateral) ( create )

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