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Original research
Molecular confirmation that fibrocartilaginous dysplasia is a variant of fibrous dysplasia
  1. Juan Zhou1,2,
  2. Xuling Su1,2,
  3. Dingjun Hu3,
  4. Li Zhang1,2,
  5. Chunyan Chen1,2,
  6. Keyang Sun1,2,
  7. Huizhen Zhang1,2,
  8. Zhiyan Liu1,2
  1. 1Department of Pathology, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
  2. 2Comprehensive Oncology Center of Bone and Soft Tissue, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, Shanghai, China
  3. 3Department of Radiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
  1. Correspondence to Professor Zhiyan Liu, Department of Pathology, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China; zhiyanliu{at}shsmu.edu.cn

Abstract

Aims Fibrocartilaginous dysplasia (FCD) is a subvariant of fibrous dysplasia (FD). This study aims to retrospectively elucidate the clinicopathological and separate genetic features of the cartilaginous and fibro-osseous components of FCD.

Methods In total, 24 patients (14 men and 10 women) with FCD were included in our cohort. The diagnosis was confirmed morphologically and immunohistochemically, and genetic features were determined via Sanger sequencing.

Results Five patients were polyostotic, and 19 were monostotic, predominantly concerning the femur. Radiography revealed a well-demarcated ground glass appearance with ring-like or scattered calcification. Histologically, the lesions were characterised by proliferative fibroblasts, immature woven bone and highly differentiated hyaline cartilage. The fibro-osseous components exhibited positive immunoreaction with SATB2 and a low Ki-67 proliferation index. The fibro-osseous and cartilaginous components shared mutations at codon 201 in exon 8 of the guanine nucleotide-binding protein/a-subunit (GNAS) gene, specifically CGT>CAT (p.R201H) in four patients and the wild-type isocitrate dehydrogenase (IDH)1/IDH2 gene. Telomerase reverse transcriptase (TERT) promoter mutations (C288T and C229G) occurred in both fibro-osseous and cartilaginous components in two patients.

Conclusions FCD encompasses areas of conventional FD with additional cartilage. Importantly, the presence or absence of mutations in the GNAS gene and/or the TERT promoter is common between the fibro-osseous and cartilaginous components of the disease. These results further confirmed FCD as a variant of FD.

  • pathology, molecular
  • bone neoplasms
  • morphological and microscopic findings

Data availability statement

The processed data required to reproduce the above findings are available by email.

https://doi.org/10.1136/jcp-2024-209626

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    Data availability statement

    The processed data required to reproduce the above findings are available by email.

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    Footnotes

    • Handling editor Vikram Deshpande.

    • JZ and XS contributed equally.

    • Contributors JZ identified and screened the fibrocartilaginous dysplasia cases, and provided histopathology data. XS interpreted the molecular data and wrote the original draft. JZ, CC and HZ conducted the evaluation of H&E-stained sections from these cases. DH reviewed the preoperative radiological images. LZ and KS performed the immunohistochemical staining and Sanger sequencing. ZL designed, led and funded the project, and revised the manuscript. ZL is the guarantor.

    • Funding This work was funded by Programmes of National Natural Science Foundation of China (81972500), Science and Technology Innovation Plan of Science and Technology Commission of Shanghai Municipality (grant no. 20Z11900304), Nature Science Fund of Science and Technology Commission of Shanghai Municipality (grant no. 23ZR1448200), clinical research funds from Shanghai Jiao Tong University Affiliated Sixth People's Hospital (ZL 2020).

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.