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

Aims Fibrocartilaginous mesenchymoma is a rare intraosseous lesion with a total of 25 cases described in the literature. This study describes the clinical, radiological, and histological features of eight new cases of fibrocartilaginous mesenchymoma collected at a single institution between 1982 and 2016. The presence of GNAS and IDH1/2 mutations and MDM2 amplification was explored to evaluate possible links between fibrocartilaginous mesenchymoma, fibrous dysplasia, dedifferentiated chondrosarcoma, and low-grade osteosarcoma. Methods and results Eight new cases of fibrocartilaginous mesenchymoma of bone identified in our archives, dating from 1982 to 2016, were reviewed. The diagnosis was not performed on the initial biopsy in any of these cases, mainly due to the absence of obvious cartilaginous differentiation. On imaging, the tumour contained cartilaginous calcifications and showed a very strong uptake of contrast medium after injection. Histologically, the tumour was characterized by spindle cell proliferation mimicking a low-grade spindle cell sarcoma, associated with epiphyseal growth-plate-like nodules of cartilage, and bone production. Molecularly, no GNAS and IDH1/2 mutations or MDM2 amplification were found in the cases analyzed. Only one case recurred one year following intralesional resection. None died of disease. Conclusions 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 genetically related to fibrous dysplasia, low-grade osteosarcoma, and dedifferentiated chondrosarcoma.