Fibrocartilaginous mesenchymoma of bone: a single‐institution experience with molecular investigations and a review of the literature

Abstract

This very rare bone tumour has a typical radiological and histological pattern and a favourable survival outcome after treatment. Local recurrences can be prevented with complete surgery. Fibrocartilaginous mesenchymoma does not seem to be related genetically to fibrous dysplasia, low-grade osteosarcoma and de-differentiated chondrosarcoma.

Fibrocartilaginous mesenchymoma with an unusual location in the rib

“…Rare cases of FCD demonstrate enchondral ossification as in FM; however, FCD principally consists of bland spindle cells and characteristic, irregular, curvilinear trabeculae of woven bone, lacking osteoblastic rimming. Furthermore, GNAS mutations are detected in many cases of FCD, whereas no specific molecular aberrations have been found in FM [2]. Although the GNAS mutation was not tested in the present case, differentiation from FCD was not difficult due to the tumor's overall histological characteristics.…”

“…Since then, there have been debates in the literature regarding FM as a separate neoplasm or one that coincides with FCD [5][6][7]. However, several studies, particular-ly molecular analyses, have demonstrated that FM is not genetically related to FCD, which has a characteristic GNAS (guanine nucleotide-binding protein α-stimulating polypeptide) mutation [2]. Accordingly, the 5th edition of the World Health Organization classification of bone tumors newly listed FM as an independent tumor entity [8].…”

“…FM predominantly affects long bones, including the femur, tibia, and humerus; a few cases have been reported in rare locations, such as metatarsus, iliac-pubic bones, vertebrae, and ribs [2]. FM tends to affect young patients aged 3 months to 27 years (median age of 13 years), with a slight predominance of male patients.…”

“…Fibrocartilaginous mesenchymoma (FM) is a rare, locally aggressive bone tumor, with fewer than 35 cases reported in the literature since 1984 when it was first reported by Dahlin et al [1][2][3]. FM predominantly affects young patients with a median age of 13 years.…”

Updates from the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours

“…Histologically, it is composed of mildly atypical spindle cells admixed with nodules of hyaline cartilage that have a ‘growth plate‐like’ appearance and undergo endochondral ossification. In a recent small series, GNAS and IDH1 / 2 mutations were absent, as was MDM2 amplification, providing molecular support for fibrocartilaginous mesenchymoma being distinct from several other entities that show overlapping morphology (fibrocartilaginous dysplasia, chondrosarcoma, and low‐grade osteosarcoma, respectively) 100 …”