Ossifying fibromyxoid tumours: A case series

Abstract

Background: Ossifying fibromyxoid tumour is a rare mesenchymal soft tissue sarcoma with uncertain differentiation and variable metastatic potential.

Patients and methods: This study offers a retrospective analysis of 23 patients diagnosed with OFMT between 1993 and 2024.

Results: The tumours most commonly arose in the extremities and trunk, with all patients undergoing surgical resection of the primary tumour. Immunohistochemical analysis frequently revealed the expression of S100 protein and desmin, while next-generation sequencing identified PHF1 rearrangements in 83 % of patients with available NGS, notably PHF1::EP400 and PHF1::TFE3 fusions. Five patients experienced local recurrence, and four developed metastatic disease. There is no prospective data to guide decision making with regards to systemic therapy, and doxorubicin-based regimens demonstrate limited efficacy. However, the potential role of epigenetic dysregulation in OFMT tumorigenesis opens exciting avenues for treatment. In this cohort, one patient exhibited a remarkably durable response to a combination of gemcitabine, which inhibits DNA methylation, and dacarbazine, following rapid tumour progression on doxorubicin.

Conclusions: Given the limited clinical experience with OFMT, multidisciplinary tumour boards are crucial for tailoring individualized treatment strategies. This study contributes to the growing body of literature on OFMT, providing a foundation for future research.

Keywords: Case series; Epigenetics; Ossifying fibromyxoid tumour; Rearrangements; Soft tissue sarcoma.