Table 1.

Results of tumour testing for the two patients with follicular dendritic cell sarcoma

Patient	Institutions reviewing pathology	IHC positive staining	Molecular testing performed	TMB (Muts/Mb) or MMR testing	PD-L1 testing	Mutations observed	# of cycles of checkpoint inhibitors	Prior systemic therapy
1	A, B, D	CD21 CD35 CD23 CD4 Inhibin Vimentin	Foundation Hem	Low (4)	Combined score 60%–70%	ARFRP1, ATR, AURKA, CCND2, FGF23, FGF6, GNAS, KDM5A, NFKBIA, SRC, TOP1, ZNFF217	8	VAdrC
2	B, C, E	CD21 CD35 CD23 CD4 Inhibin	Caris Life Science	MMR Sufficient	2+, combined score 10%	‘No actionable mutations’	6	None

Pathology: institutions included: A: Mt Sinai Medical Center New York, B: Northwell Health, C: New York Presbyterian Medical Center, D: Dana Farber Cancer Institute, E: Memorial Sloan Kettering Cancer Center. No translocations were found in molecular testing of patient 1; the testing for patient 2 did not include an RNA sequencing component to investigate for translocation fusion genes.

IHC, immunohistochemistry; MMR, mismatch repair; PD-L1, programmed cell death 1 ligand; TMB, tumour mutation burden; VAdrC, vincristine, doxorubicin, cyclophosphamide.