|Year : 2017 | Volume
| Issue : 5 | Page : 503-504
Fibrocartilaginous dysplasia: A rare but distinct entity
HL Kishan Prasad
Department of Pathology, K. S. Hegde Medical Academy of Nitte University, Mangalore, Karnataka, India
|Date of Web Publication||14-Nov-2017|
H L Kishan Prasad
Department of Pathology, K. S. Hegde Medical Academy of Nitte University, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kishan Prasad H L. Fibrocartilaginous dysplasia: A rare but distinct entity. Med J DY Patil Univ 2017;10:503-4
Fibrous dysplasia (FD) is a rare skeletal lesion with benign, localized intramedullary proliferation of trabecular woven bone admixed with fibrous tissue. It may present as monostotic, involving one bone, or polyostotic, involving several bones. In addition to these fibrous and bony components, the lesion may show small and irregular benign cartilage in histopathology. Lesions with massive chondroid differentiation in FD are extremely rare and are termed as fibrocartilaginous dysplasia (FCD).,, In the world literature, there are very few original studies about this rare entity, but many case reports are being published.
FCD is a genetic noninherited condition caused by missense mutation in the guanine nucleotide-binding protein/α-subunit-1 gene on chromosome 20. The polyostotic variant usually is associated with endocrine dysfunction, abnormal pigmentation, and precocious puberty in girls (McCune–Albright syndrome).,, It is seen in patients between the ages of 4–26 years and mostly located in the proximal femur.,, A few unusual sites such as proximal tibia, distal femur, skull bones, and upper extremities involving ulna, radius, humerus, and phalanges are being reported.,,,,, These patients are usually asymptomatic or may present with pain or pathological fractures. Radiologically, FD is usually a well-defined intramedullary and expansile lesion. It may show variation in the density ranging from radiolucent to radiodense, depending on the relative proportions of the fibrous and osseous tissue.,,, Radiological and histopathological findings in most of the cases are straightforward, without any diagnostic dilemmas. Typical cases are characterized by the spindle cells embedded in fibrous stroma along with irregularly shaped trabeculae of immature bone (termed as Chinese letter pattern) in place of normal bone and marrow.,,, Few cases on histology show small and irregular foci of cartilage. However, FCD shows large foci of cartilage. Histogenesis of this cartilage may be intrinsic to the lesion itself, or secondary to fracture, or may result from disruption of an affected growth plate during childhood.,, Some people believe that it is originated from prolonged columns of the epiphyseal growth plate. At places, these chondrocytes may extend deep into the metaphyseal bone. Some authors proposed that these cartilaginous islands arose as developmental rests from epiphyseal cartilage and this cartilage tissue developed simultaneously with FD.,,, These are commonly seen with the polyostotic variant of FD., The craniofacial bones mostly show intramembranous ossification; hence, the infrequency of FCD in this site is not surprising., Some believe that the small irregular foci of cartilage are remnants of a previous fracture callus., Lack of awareness about this distinct entity may lead to erroneous diagnosis of chondromatous neoplasm and even a chondrosarcoma due to these large, tumor-like nodules of cartilage., The amount of this cartilage tissue is widely variable, ranging from small microscopic foci to radiographically evident extensive areas of hyaline cartilage, sometimes resembling a primary cartilage neoplasm. Few cases show stippled calcifications. Most of these cases were located in the trochanteric area of the proximal femur. This was in contrast to typical FD, which has a predilection for craniofacial bones.,,
The differential diagnosis includes enchondroma, dedifferentiated chondrosarcoma, Ollier's disease, chondrosarcoma secondary to FD, intramedullary osteosarcoma, and fibrocartilaginous mesenchymoma. Radiological findings and histology of the benign fibro-osseous areas in addition to clinical correlation are vital to the diagnosis.,,
Treatment consists of curettage and correction of deformities and fractures. Described treatment options for fibrocartilaginous dysplasia include observation, curettage with bone grafting, intramedullary nailing, and en bloc excision. GNAS mutation analysis is now being incorporated for the diagnosis of fibro-osseous craniofacial and long bone lesions with considerable sensitivity and specificity. This mutation is also described in parosteal osteosarcoma, stating that molecular diagnostics are to be used judiciously and in correlation with clinicopathologic parameters.,,,
In conclusion, FD is a common benign fibro-osseous entity having a spectrum of histological appearances. Enchondroma-like areas further complicate the picture. Although the femoral neck region is the most frequent location for this latter variant, other bony areas close to the epiphyseal plate can theoretically contribute to FCD. It is necessary to make a careful diagnosis based not only on the pathological findings but also on imaging and clinical findings to rule out the differential diagnoses. Reporting these rare cases will help us analyze the clinicopathological aspects better and could show promise in exploring the enigma of FCD.
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