Fibrous Dysplasia with Massive Cartilaginous Differentiation (Fibrocartilaginous Dysplasia) in the Proximal Femur: A Case Report and Review of the Literature

Abstract

Fibrous dysplasia (FD) is a monostotic or polyostotic benign bone lesion with spindle-cell proliferation in woven bone and stroma. Rarely, cartilaginous differentiation can be seen in the lesions of FD. FD with massive cartilaginous differentiation is called fibrocartilaginous dysplasia (FCD) and is considered a rare variant of FD. Although pathological findings of FD show irregular immature bone formation without osteoblastic rimming in fibrous tissue, and rarely show very small amounts of cartilage, histological images of FCD are said to show that cartilage with a relatively high cell density is present in the majority and that FD-like findings are seen in parts of it. The most characteristic feature of FCD on images is calcification in the lesions reflecting cartilaginous tissue. On the other hand, typical radiographic findings of FD include shadows with a ground-glass appearance and thinning and bulging of the cortical bone, the observation if calcification is not usual. Therefore, in the diagnosis of FCD, differentiation from multiple enchondromatosis, Ollier disease, chondrosarcoma, and chondrosarcoma secondary to FD is necessary, and it seems important to make a careful diagnosis based not only on the pathological findings but also on imaging and clinical findings. Herein, we report on a case of FD of the proximal femur associated with intralesional extensive carti laginous differentiation in which a pathological fracture occurred during follow-up, with a review of the literature.

Keywords: Cartilaginous differentiation; Fibrocartilaginous dysplasia; Fibrous dysplasia; Proximal femur.

Fig. 1

Plain radiography. a A ground-glass appearance with marked calcification and a pathological minor fracture in the right proximal femur. b Multiple ground-glass appearances in the skull.

Fig. 2

MRI. a Isointensity with punctate low signal intensity on T1-weighted images. b Irregular high signal intensity on T2-weighted images. c Irregular peripheral predominant enhancement on Gd contrast-enhanced images.

Fig. 3

Bone scintigraphy showing an accumulation of radioactivity in the right ilium, right proximal femur, right proximal ulna, and the skull.

Fig. 4

a Pathological fracture with displacement in the metaphysis of the right femur. b Artificial bone was implanted after curettage and fixed with a locking plate so that the varus of the proximal femur was corrected.

Fig. 5

Histopathological findings of the specimen. a Nodular hyaline cartilage tissue is present in the majority of the specimen without marked atypia. b Proliferation of fibroblast-like spindle cells and woven bone were evident in parts of the lesion.