Unusual immunohistochemical “null” pattern of four mismatch repair proteins in gastric cancer: A case report

Table 1 Summary of clinicopathological features of null mismatch repair immunohistochemical staining pattern reported in the literature

Case No.	Age (yr)	Sex	Location	MLH1 promoter methylation status	MSH2 status	BRAF status	Specimen tested	Ref.
1	72	Female	Colorectal cancer	Hypermethylation	Germline G587R mutation	Negative	Resection	Hagen et al[8], 2011
2	80	Female	Colorectal cancer	Hypermethylation	Three somatic mutations (MSH2 c.1861 C>T (p.R621*) in exon 12, c.298G>A (p.V100I) and c.633dupG (p.K212Efs*20)	Mutation	Resection	Wang et al[9], 2017
3	76	Male	Ascending colon	Hypermethylation	Unknown	Mutation	Biopsy	Westwood et al[10], 2019