Table 4. Clinical characteristics of dMMR tumours with low or absence of microsatellite instability and pMMR tumours with instability.

Group	Site	Histology	Age (years)a	Criteriab	No. of unstable markers (type)	MMR protein expression	MMR germline/somatic mutation	Remarks
dMMR	Colon	ADC	39	Beth	2/6 (BAT26, BAT40)	MSH6	MSH6 c.2150_2153del (p.Val717Alafs)	+Synchronous colon cancer
	Endometrium	ADC	49	Ams-II	1/6 (BAT26)	MLH1 PMS2	MLH1 somatic hypermethylation
	Endometrium	ADC	46	EC	1/6 (BAT40)	MSH6	MSH6 c.3268_3272del (p.Glu1090Lysfs)
	Endometrium	ADC	58	Ams-II	0/6	MSH6	MSH6 c.3261delC p.Phe1088Serfs
	Endometrium	ADC	57	Ams-I	0/6	N	MLH1 c.1165C>A (p.Arg389*)
	Ovary	ADC	49	Ams-II	2/6 (BAT40, NR22)	MSH6	MSH6 c.2277_2281dup (p.Arg761Lysfs)
	Urothelium	Carcinoma	48	Ams-I	2/6 (BAT26, NR27)	MLH1 PMS2	MLH1 c.2117_2130del (p.Gly706Valfs)
	Urothelium	Carcinoma	53	EC	2/6 (BAT40, NR22)	N	MSH6 c.3080dupT (p.Ser1028Ilefs)	+Endometrial carcinoma at 53
	Urothelium	Carcinoma	56	Ams-I	1/6 (BAT40)	MSH2 MSH6	MSH2 c.1022T>C (p.Leu341Pro)c	+Colorectal adenoma at 56
	Rectum	Adenoma	51	—	1/6 (BAT40)	MSH2 MSH6	MSH2 c.793-2A>C (p.Val265_Gln314del)	+Multiple sebaceous carcinomas at 51
	Rectum	Adenoma	56	Ams-I	0/6	N	MSH2 c.1022T>C (p.Leu341Pro)c	+Urothelial carcinoma at 56
pMMR	Skin	Sebaceous adenoma	54	EC	2/6 (BAT26, BAT40)	N	ND	+Multiple sebaceous adenomas at <54+past history of ovary carcinoma at 44
	Rectum	Adenoma	48	—	2/6 (BAT25, BAT40)	N	ND

Abbreviations: ADC=adenocarcinoma; dMMR=defective DNA mismatch repair; EC=extended criteria; N=normal expression of the four DNA mismatch repair (MMR) proteins; ND=not determined; pMMR=proficient MMR.

^aAge at diagnosis.

^bAms, Amsterdam criteria: Ams-I ( Vasen et al., 1991), Ams-II (Vasen et al., 1999); Beth, revised Bethesda criteria (Umar et al., 2004); EC Lynch Syndrome-related cancer <60 years (Olschwang et al., 2004; French National Cancer Institute guidelines).

^cMutation c.1022T>C is classified as pathogenic (UMD MSH2 mutations database: http://www.umd.be/MSH2/).