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fibrocartilaginous dysplasia

Monday 6 June 2011

Digital case

- Case 200 (HPC:200) : Fibrocartilaginous dysplasia (fibrous dysplasia with chondroid differentiation)

Definition: Fibrocartilaginous dysplasia is a variant of fibrous dysplasia in which extensive cartilaginous differentiation is identified. The amount of cartilage varies from case to case, however, no percentage has been proposed to consider this diagnosis. It is a variant of fibrous dysplasia.

No percentage of cartilage in FD has mentioned by other authors in order to consider the diagnosis of FCD, but in our case 60% of the lesion was composed by hyaline cartilage.

The important thing is to be aware of the possibility of finding extensive cartilaginous areas in an otherwise typical lesion of monostotic or polyostotic fibrous dysplasia and thus avoiding misdiagnosing it as a cartilaginous neoplasia.

Synopsis

- lucent lesion
- ill-defined borders
- well maintained cortex
- Computed tomography scan:

  • increased density of the medullary cavity
  • cortex intact.

Microscopy

- cartilaginous component

  • increased cellularity
  • some chondrocytes display moderate atypia and binucleation,

- fibro-osseous component

- Areas of endochondral ossification
- Areas of calcification.

It is well recognized that fibrous dysplasia (FD) may contain cartilage, the
amount of which, however, is quite variable.

Lichtenstein and Jaffe in their original article of fibrous dysplasia recognized
that cartilage was “an integral part of the dysplastic process.”

Despite cases of FD detailing the occurrence of cartilage have been reported since 1930, the first description of FCD as a variant of fibrous dysplasia was made by Pelzmann et al.9 in a 20-year-old man with well
documented history of polyostotic fibrous dysplasia. The
term used by Pelzmann was fibro-chondrodysplasia, pointing out that documentation of malignant behavior was lacking in the scattered reports of chondrosarcomas complicating fibrous dysplasia and suggested that many of those cases represent examples of FCD.

In an excellent review of the English literature, Kyriakos et al. found forty-one cases of FD in which cartilaginous differentiation was indicated radiographically, grossly or histologically. Kyriakos maintains that since foci of cartilage are well recognized as part of fibrous dysplasia and occur along a quantitative spectrum, FCD represents the extreme end of cartilaginous differentiation in fibrous dysplasia.

Under the title “fibrocartilaginous dysplasia” or “fibrochondrodysplasia”, 11 cases have been reported in the literature
to 2006.

No gender dominance has been found, and the age of presentation ranged from 4 to 53 years. The proximal portion of the femur is the most common site of FCD, although tibial and ischion involvement was seen in one case respectively, and involvement of the femoral shaft was seen in another case. The presenting symptom is pain, deformity or a mass. However, patients can also be asymptomatic. Three patients had an associated polyostotic form of fibrous dysplasia.

Radiologically, the lesion is generally well-demarcated and shows ground-glass opacity. Cortical expansion can be seen, however, the cortex is always intact. Stippled or ringlike calcifications suggesting chondroid elements can also be present.

Macroscopically, the appearance of the lesion is similar to that of enchondroma or low-grade chondrosarcomas, and consists of fragments or irregular masses with an obvious cartilaginous appearance.

The histological appearance of FCD consists of large lobules of cartilage surrounded by fibro-osseous tissue with features typical of fibrous dysplasia. The cartilaginous component may be massive. In these cases, large dysplastic cartilaginous islands may be misinterpreted as benign or even malignant cartilaginousneoplasms. Increased cellularity and atypical chondrocytes may be present, and focal enchondral ossification is usually seen in the majority of cases. However, the key to a correct diagnosis is the identification of the classical component of fibrous dysplasia.

Differential diagnosis

The differential diagnosis of FCD includes:
- enchondroma
- chondrosarcoma
- well-differentiated intramedullary osteosarcoma
- fibrocartilaginous mesenchymoma.

Enchondroma is a common benign cartilaginous tumor that occurs most frequently in small bones of the hands and feet, particularly the proximal phalanges. Histologically, it is composed of mature lobules of hyaline cartilage. Foci of myxoid degeneration, calcification, and endochondral ossification are common.

Chondrosarcoma in childhood is distinctly uncommon. The risk of chondrosarcoma is increased in children with enchondromatosis syndromes (e.g. Ollier`s disease, Maffucci`s syndrome, metachondromatosis) and in those with hereditary multiple exostosis.

Most malignant bone tumors in this age group exhibiting cartilage formation actually correspond to osteosarcomas with predominant cartilaginous component.

Chondrosarcoma comprises 5% or fewer of all primary malignant skeletal tumors in the first two decades of life. Three variants of chondrosarcoma are recognized in children: mesenchymal, clear cell, and
myxoid. Histologically, these variants of chondrosarcoma lack the fibroosseous component characteristic of fibrous dysplasia.

In the case of well-differentiated intramedullary osteosarcoma most patients are adults, the femur and tibia being the most commonly affected sites. Histological features simulating fibrous dysplasia and small foci of atypical cartilage may be present. However, areas of high-grade pleomorphic osteosarcoma can be found.

Fibrocartilaginous mesenchymoma is an extremely rare lesion that tends to affect the metaphyseal region of bones, particularly the proximal fibula. The lesion contains fibrous areas and islands of cartilage that show a pattern of organization reminiscent of epiphyseal growth plates. It is locally aggressive with a high frequency of recurrence, especially when resection is incomplete.

See also

- fibrous dysplasia of bone

Open access references

- A patient with focal fibrocartilaginous dysplasia in the distal femur and review of the literature. Ando A, Hatori M, Hosaka M, Hagiwara Y, Kita A, Ochiai T, Itoi E. Tohoku J Exp Med. 2008 Aug;215(4):307-12. PMID: 18679004 [Free]

- Fibrocartilaginous dysplasia (fibrous dysplasia with extensive cartilaginous differentiation). Vargas-Gonzalez R, Sanchez-Sosa S. Pathol Oncol Res. 2006;12(2):111-4. PMID: 16799714 [Free]