AIMS: Ossifying fibromyxoid tumour is a rare mesenchymal neoplasm predominantly affecting adults characterised by a multinodular growth pattern and the presence of a fibrous pseudocapsule with areas of ossification. Prompted by the recognition of a non-ossifying ossifying fibromyxoid tumour with lipomatous differentiation which caused diagnostic difficulty, we sought to further explore cases of ossifying fibromyxoid tumour with non-osseous heterologous elements. METHODS AND RESULTS: A search of our institutional and consultation archives revealed three additional cases that demonstrated lipomatous components and two cases with cartilaginous differentiation. RNA-sequencing revealed fusions involving PHF1 (n = 4) or EPC1 (n = 1) in all (five of five) cases tested, including EPC1::PHC1 and JAZF1::PHF1 fusions, which have not been reported before in ossifying fibromyxoid tumour. CONCLUSION: These six cases expand the histomorphological spectrum of ossifying fibromyxoid tumour, introducing lipomatous differentiation as a hitherto undocumented feature. Awareness of these rare variants will ensure appropriate diagnosis and clinical management.

• Klíčová slova
• OFMT, cartilaginous differentiation, chondroid differentiation, lipoblasts, lipomatous differentiation, ossifying fibromyxoid tumour, soft tissues,
• MeSH
• buněčná diferenciace MeSH
• chrupavka patologie   MeSH
• diferenciální diagnóza MeSH
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• lipom * patologie   diagnóza   genetika   MeSH
• nádory měkkých tkání * patologie   diagnóza   genetika   MeSH
• osifikující kostní fibrom * patologie   diagnóza   genetika   MeSH
• senioři MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH