Pathology: ossifying fibromyxoid tumour

Ossifying fibromyxoid tumour

• Circumscribed; lobulated; loose fascicles of spindle-stellate cells

• Eosinophilic cytoplasm

• Round-ovoid euchromatic nuclei; inconspicuous mitotic activity

• Myxoid-collagenous stroma with "starburst" patterns

• IHC: S100, TFE3

• RNA-seq: PHF1::TFE3 gene fusion

Ossifying fibromyxoid tumour

• Circumscribed; epithelioid-spindle cells arranged in fascicles, nests and cords

• Pale eosinophilic cytoplasm

• Round-ovoid nuclei with small nucleoli and mild atypia; occasional mitotic activity

• Incomplete rim of metaplastic bone; hyalinized collagen arranged in bands, and "starburst" patterns

• IHC: S100

• RNA-seq: failed (presumably due to decalcification)

Ossifying fibromyxoid tumour

• Circumscribed; epithelioid-spindle cells with fascicular and reticular patterns

• Pale eosinophilic-amphophilic cytoplasm; in areas the cells contain one or two large clear vacuoles

• Round-ovoid nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

• Myxoid stroma with microcytic degeneration; hyalinized collagen with "starburst" pattern

• Ossification is not present

• RNA-seq: PHF1::TFE3 gene fusion

• PMID: 30920708

Ossifying fibromyxoid tumour

• Epithelioid-spindle cells with vague fascicular pattern

• Pale amphophilic cytoplasm

• Round-ovoid nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

• Myxoid stroma with delicate collagen fibres

• Ossification is not present

• RNA-seq: PHF1::FOXR2 gene fusion 

Ossifying fibromyxoid tumour

• Spindle cells with vague fascicular pattern

• Pale amphophilic cytoplasm with long tapering processes

• Ovoid-elongated nuclei with small nucleoli and mild atypia; inconspicuous mitotic activity

• Myxoid stroma with delicate collagen fibres

• Ossification is not present

• RNA-seq: CREBBP::BCORL1 gene fusion

• PMID: 27537276

Ossifying fibromyxoid tumour, malignant

• Epithelioid-spindle cells arranged in fascicles, nests and cords

• Pale amphophilic cytoplasm

• Round-ovoid nuclei with small nucleoli and mild atypia; conspicuous mitotic activity

• Necrosis; bands of hyalinized collagen 

• Ossification is not present

• IHC: S100

• RNA-seq: HCFC1::PHF1 gene fusion*

* To date unreported

Ossifying fibromyxoid tumour, malignant

• Epithelioid-spindle cells arranged in fascicles, nests and cords

• Pale amphophilic cytoplasm

• Round-ovoid nuclei with small nucleoli and mild atypia; conspicuous mitotic activity

• Necrosis; broad bands of hyalinized collagen 

• Ossification is not present

• IHC: S100, SATB2

• RNA-seq: ZC3H7B::BCOR gene fusion

• PMID: 24285434 

Ossifying fibromyxoid tumour, malignant

• Spindle-epithelioid cells arranged in vague fascicles

• Pale amphophilic cytoplasm with delicate tapering processes

• Hyperchromatic ovoid nuclei with mild atypia; mitotic activity

• Ossification present on imaging

• IHC: S100

• RNA-seq: CREBBP::BCORL1 gene fusion

• PMID: 27537276