Primary malignant ossifying fibromyxoid tumour of the bone. A clinicopathologic and molecular report of two cases.

OBJECTIVE

To report the exceptional occurrence of ossifying fibromyxoid tumour (OFMT) as a primary bone lesion. OFMT is a rare soft tissue tumour of uncertain differentiation and variable malignant potential, that occurs in adults with a slight male predominance. It is typically located in the subcutis or in the skeletal muscles of the extremities, followed by trunk or head and neck.

METHODS

Two cases of OFMT proven to arise from bone are presented. The first is a 65-year old female with a history of rib "osteosarcoma", presenting with an inferior lobe left lung mass. The second is a man with a lytic lesion of the 5th cervical vertebra that recurred shortly after resection. Following H&E and immunohistochemical examination, tumour samples were analysed by NGS and by break-apart FISH to detect rearrangement of the and genes.

RESULTS

gene-rearrangement was identified by FISH on both the primary and the metastatic lesion of first patient. NGS identified a (intron1) and (exon 10) fusion transcript later confirmed by positive rearrangement on FISH in the second case.

CONCLUSIONS

The demonstration of gene rearrangements represents a fundamental ancillary diagnostic test when presented with challenging examples of OFMT.