Article Figures & Data
Figures
- FIG 1.
Spinal mesenchymal chondrosarcoma with HEY1-NCOA2 fusion gene in a 16-year-old girl. Sagittal and axial MR images (A–C) reveal a lobulated well-circumscribed mass in the extradural space of the cervical spine extending along the left neural foramen (arrow). Lesion shows an isointense signal on T1-weighted image (A), with homogeneous contrast enhancement (B) and areas of signal drop-out on axial gradient image (C). Amorphous calcification noted within the tumor on axial CT (D, arrow). H&E revealed spindle cell morphology with abrupt areas of cartilage formation (E, arrows). Tumor showed positive staining for CD99 and SATB2 (F) on immunohistochemistry. Molecular testing confirmed the presence of a HEY1-NCOA2 gene fusion event in the tumor, further confirming a diagnosis of mesenchymal chondrosarcoma. The HEY1-NCOA2 fusion is most frequently observed in mesenchymal chondrosarcomas.
- FIG 2.
Metastatic solitary fibrous tumor in a 69-year-old woman. MR images (A–D) depict a large multilobulated mass along the inferior tentorial surface (arrow) with avid contrast enhancement and adjacent cerebellar edema. Smaller similar nodules are noted along the superior tentorial surface and along right cerebellar convexity (B and D, arrows). Osseous and pulmonary metastatic deposits with increased uptake seen on FDG-PET study (E, arrows). The tumor cells show nuclear expression of STAT6 (F), compatible with the presence of NAB2-STAT6 fusion and diagnostic of solitary fibrous tumor.
- FIG 3.
Intracranial inflammatory myofibroblastic tumor in a 35-year-old man. Multiple axial MR images (A–C) reveal a lobulated mass (arrows) in the left basifrontal region with extensive vasogenic edema in the adjacent parenchyma, disproportionate to the size of the mass (A). Lesion shows foci of signal drop-out (hemorrhage) on SWI (B) and heterogeneous enhancement (C). Lesion shows increased uptake on FDG-PET examination (D). Rapid increase in the size of the mass was noted in the follow-up MRI after 3 months with clinical deterioration (Supplemental Data). Surgical resection was performed with histopathology revealing epithelioid inflammatory myofibroblastic tumor. Immunohistochemistry depicted perinuclear anaplastic lymphoma kinase staining, correlating with the presence of RANBP2-anaplastic lymphoma kinase gene fusion (Supplemental Data).
- FIG 4.
Intracranial mesenchymal tumor, FET::CREB fusion-positive in a 19-year-old man. Sagittal T1-weighted (A) and contrast-enhanced (B) images reveal a large extra-axial dural-based mass along the frontal convexity with heterogeneous enhancement. Lesion shows heterogeneous hyperintense signal on FLAIR (C) with areas of signal drop-out (calcification) on SWI (arrow) (D). Histopathology demonstrated a low-grade mesenchymal neoplasm with clear cell features and fibrillary deposits. Further molecular characterization by targeted next generation sequencing (sarcoma targeted gene fusion/rearrangement panel) revealed FET::CREB fusion.
- FIG 5.
Spinal CIC-rearranged sarcoma in a 14-year-old boy. MR images depict a small well-circumscribed peridural mass in the midthoracic region (arrows) with isointense T1 signal (A), hyperintense T2 signal (B), and avid contrast enhancement (C). The tumor extends through the left neural foramen into the paraspinal space with mass effect on the cord. Tumor shows increased uptake on FDG-PET study (arrow) (D). Histopathology (Supplemental Data) revealed sarcomatous cells with neoplastic cells positive for cyclin and calretinin immunohistochemical stains. Molecular cytogenetic studies (fluorescence in site hybridization) showed balanced rearrangement of the CIC locus in 91% of the nuclei (181/200).
- FIG 6.
Primary intracranial sarcoma, DICER1-mutant, in a 15-year-old girl. MR images depict a small well-circumscribed extra-axial dural-based mass along the left frontal convexity with buckling of the underlying cortex (arrows). Tumor shows hypointense T1 signal (A), hyperintense T2 signal (B), and avid contrast enhancement (C). Multiple foci of signal drop-out noted on SWI suggest hemorrhagic foci. Histopathology (Supplemental Data) demonstrates cellular composition of spindled and pleomorphic tumor cells with high mitotic activity. The tumor cells are positive for MyoD1 (patchy, focal), and negative for desmin on immunohistochemistry. “Somatic disease/germline comparator exome” sequencing panel showed pathogenic germline variant for DICER1. Overall, the histomorphologic, immunophenotypic, and genetic findings are diagnostic of primary intracranial sarcoma, DICER1-mutant.
Tables
New World Health Organization 2021 classification of CNS mesenchymal tumors and their molecular markers
Mesenchymal, Non-Meningothelial Tumors Involving the CNS Soft tissue tumors Fibroblastic and myofibroblastic tumors Solitary fibrous tumor Partially or completely lack STAT6 nuclear expression on immunohistochemistry Vascular tumors Hemangiomas and vascular malformations Diagnostic molecular pathology is not clinically relevant Hemangioblastoma Skeletal muscle tumors Rhabdomyosarcoma PAX3::FOXO1 or PAX7::FOXO1 fusion in alveolar subtype, with a worse prognosis Tumors of uncertain differentiation Intracranial mesenchymal tumor, FET::CREB fusion-positive Diagnostic FET::CREB family gene fusions CIC-rearranged sarcoma CIC gene fusion and up-regulation of ETV complements Primary intracranial sarcoma, DICER1-mutant DICER1 mutations with DNA-methylation profile distinct Ewing sarcoma Definitive diagnosis requires confirmation of FET::ETS–type gene fusion Chondro-osseous tumors Chondrogenic tumors Mesenchymal chondrosarcoma HEY1::NCOA2 gene fusion Chondrosarcoma IDH mutation (approximately 60%) Notochordal tumors Chordoma SMARCB1 deletions in poorly differentiated chordomas Emerging entities Spindle cell carcinoma, NTRK-rearranged Frequently having GJA4 p.Gly41Cys mutations Dural angioleiomyoma NTRK1/2/3 gene fusions with DNA-methylation profile distinct Note:—ETV indicates ETS Variant Transcription Factor.
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