Solid and cystic spaces
Fibrous septa containing fibroblasts with a fascicular pattern; monomorphic ovoid nuclei; inconspicuous mitotic activity
Intervening stroma contains osteoclast-type giant cells, osteoid deposition with osteoblasts, and occasional siderophages
RNA-seq: PAFAH1B1::USP6 gene fusion
Solid and cystic spaces
Fibrous septa containing fibroblasts, with fascicular pattern; monomorphic ovoid nuclei with prominent nucleoli; inconspicuous mitotic activity
Intervening stroma contains osteoclast-type giant cells, osteoid deposition with osteoblasts, and occasional siderophages
Cystic spaces filled with blood separated by fibrous septa
Septa contain fibroblasts with fascicular pattern; monomorphic ovoid nuclei; inconspicuous mitotic activity
Intervening stroma contains osteoclast-type giant cells, woven bone rimmed by osteoblasts, and so-called "blue bone"
RNA-seq: KLF3::USP6 gene fusion
Cystic spaces filled with blood separated by broad fibrous septa
Septa contain fibroblasts with fascicular pattern; monomorphic ovoid nuclei with prominent nucleoli; inconspicuous mitotic activity
Intervening stroma contains osteoclast-type giant cells, woven bone rimmed by osteoblasts, and extravasated erythrocytes with occasional siderophages
RNA-seq: TAF7::USP6 gene fusion*
* To date unreported in the literature
Focal cyst lining
Fibrous septa containing fibroblasts with fascicular pattern; monomorphic ovoid nuclei; inconspicuous mitotic activity
Stroma contains osteoclast-type giant cells, woven bone rimmed by osteoblasts, and so-called "blue bone"