Table 2.

Mucinous borderline tumor (MBOT) and mucinous carcinoma (MOC) cases from the Genomic Analysis of Mucinous Tumors (GAMuT) cohort with discrepancies between p53 immunohistochemistry (IHC) and TP53 mutation status by sequencing.

Case	Tumor type	Detected mutation	AF	Method	IHC result	IHC source	Possible explanations
C1454	MBOT	p.V216L	0.31	SureSelect panel	Normal	TMA (then full)	IARC: missense Clinvar: likely pathogenic False negative normal IHC
C1961	MOC	p.Q375*	0.37	SureSelect panel	Normal	TMA (then full)	Late truncating mutation expressing nonfunctional protein as false negative normal IHC
C1981	MOC	p.R156H	0.36	SureSelect panel	Normal	TMA (then full)	IARC: missence Clinvar: VUS
15404	MOC	NMD	NA	Exome	Abnormal OE90	Full	Clear IHC signal: suboptimal sequencing, mutation in something other than p53 that influences p53 expression
VOA3937	MOC	NMD	NA	Exome	Abnormal OE90	Full	Clear IHC signal: suboptimal sequencing, mutation in something other than p53 that influences p53 expression
WM1070	MOC	NMD	NA	Exome (unpaired)	Abnormal OE70 (MOC) WT (MBOT)	Full	False positive IHC; tumor heterogeneity
C885	MOC	NMD	NA	SureSelect panel	Abnormal CA100	TMA (then full)	Clear IHC signal: FN sequencing, undetected large deletion

AF = allele frequency. TMA = tissue microarray. IARC = International Agency for Research on Cancer. VUS = variant of uncertain significance. NMD = no mutation detected. NA = not applicable. OE = overexpression. CA = complete absence.