Frequent mutations of the CA simple sequence repeat in intron 1 of EGFR in mismatch repair-deficient colorectal cancers

Table 1 Allelic and genotype distribution of EGFR CA-SSR I polymorphism in normal tissues of patients with colorectal tumors n (%)

	CA-SSR I status of the tumora
Genotypes	CA-SSR I MSI	CA-SSR I MSS	Total
in normal colon	(n = 36)	(n = 50)	(n = 86)
14/20	1 (2.8)	0 (0)	1 (1.2)
15/20	1 (2.8)	0 (0)	1 (1.2)
16/16	10 (27.8)	14 (28)	24 (27.9)
16/17	2 (5.6)	2 (4.0)	4 (4.7)
16/18	4 (11.1)	11 (22.0)	15 (17.4)
16/19	0 (0)	1 (2.0)	1 (1.2)
16/20	6 (16.7)	9 (18)	15 (17.4)
16/21	0 (0)	2 (4.0)	2 (2.3)
17/20	0 (0)	1 (2.0)	1 (1.2)
18/18	2 (5.6)	2 (4.0)	4 (4.7)
18/19	1 (2.8)	0 (0)	1 (1.2)
18/20	2 (5.6)	3 (6.0)	5 (5.8)
18/21	1 (2.8)	1 (2.0)	2 (2.3)
19/21	1 (2.8)	0 (0)	1 (1.2)
20/20	4 (11.1)	3 (6.0)	7 (8.1)
20/21	1 (2.8)	0 (0)	1 (1.2)
21/21	0 (0)	1 (2.0)	1 (1.2)

^aP = 0.673, CA-SSR I MSI vs CA-SSR I MSS according to the allele lengths (patients with at least one allele ≥ 20 CA (17/19) vs both alleles < 20 CA (19/23), respectively) (χ² test).