Table 2 Summary of H3K27me3-deficient dedifferentiated chondrosarcoma

Clinicopathological findings						Immunohistochemistry		Genetics	Chemotherapy/ radiotherapy	Clinical course
Case	Age/sex	Primary site	Component	Histology	Heterol. diff.	H3K27me3	SUZ12			Local Rec	Distant Met	Outcome
1	65/F	Lt 8th rib	WD	G1,2,3	—	Ret	Focal	Insuff, EED wildtype (1)	Yes/ No	No	Lung (3 m)	DOD (11 m)
			DD	MPNST-like	RMS	Lost	Focal	EED W263* (1), CDKN2A homodel
2	77/F	Lt humerus	WD	G1,2,3	—	Ret	Focal	IDH2 R172S, COL2A1 G924fs*10	No/ No	No	Lung (2 y 1 m)	NED (2 y 6 m)
			DD	MPNST-like	OS	Lost	Diffuse	IDH2 R172S, TP53 V216M
3	67/M	Lt 7^th rib	WD	G1,2	—	Ret	ND	ND	No/ No	NA (2)	Lung (1 m)	DOD (5 m)
			DD	MPNST-like	No	Lost	Focal	Insuff
4	62/F	Rt rib	WD	G2	—	Ret	ND	COL2A1 P212fs*27	Yes/ No	No	Lung (2 y 5 m)	AWD (4 y)
			DD	MPNST-like	No	Lost	Lost	SUZ12 R196fs4, NF1* G629R, TP53 P153fs*28 (few)
5	70/F	Thoracic vertebra	WD (Pri)	G1,2	—	ND	ND	COL2A1 W1224fs19 (few), CDKN2A* Y129* (few)	No/No	No	Liver (20 y)	AWD (21 y)
			WD (Met)	G2,3	—	Ret	Focal	COL2A1 W1224fs19, CDKN2A* homodel
			DD (Met)	MPNST-like	RMS, OS	Lost	Lost	COL2A1 W1224fs19, CDKN2A* homodel, SUZ12 exon 5 deletion
6	51/M (3)	Lt 7^th rib	WD	G1	—	ND	ND	ND	Yes/ No	NA (4)	No	DOD (5 m)
			DD	MPNST-like	OS	Lost	Lost	ND

Although the outcome was expressed by the time elapsed from the initial resection or biopsy in this table, the time from dedifferentiation was used for survival analysis for case 5. Only the first metastatic site was recorded
(1) Validated by Sanger sequencing
(2) Not applicable, because this patient did not undergo resection
(3) This patient had a history of multiple osteochondromas
(4) Not applicable, because this patient underwent incomplete resection
AWD alive with disease, DD dedifferentiated, DOD died of disease, F female, G grade, Heterol. diff. heterologous differentiation, Homodel homodeletion, Insuff insufficient for next-generation sequencing, Lt left, M male, Met metastasis, MPNST malignant peripheral nerve sheath tumor, NA not applicable, ND not done, NED no evidence of disease, OS osteosarcoma, Pri primary, Ret retained, RMS rhabdomyosarcoma, Rt right, WD well differentiated

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