Table 1

Frequency of skewed X inactivation (≥90:10) in patients with breast cancer

	Age group (years)
	<55				55–72			>72
	No/total	(%)	p Value*	No/total		(%)	p Value*	No/total	(%)	p Value*
Probability (p) values ⩽0.06 are in bold. Low risk patients were patients with one close relative (first or second degree) with breast cancer; high risk patients were those with two or more close relatives with breast cancer.
*Patients were compared with controls of their respective age group; p values ⩽0.017 are significant (after Bonferroni correction).
†Patients from Karolinska Hospital.
‡Patients from Huddinge Hospital and Söder Hospital.
Patients
Familial†‡	12/107	(11.2)	0.001	11/113		(9.7)	0.15	4/52	(7.7)	0.02
Low risk†‡	10/76	(13.2)	0.001	7/65		(10.8)	0.22	1/29	(3.4)	0.02
Low risk†	6/32	(18.8)	0.001	3/26		(11.5)	0.18	0/12	(0.0)	0.16
Low risk‡	4/44	(9.1)	0.06	4/39		(10.3)	0.38	1/17	(5.9)	0.23
High risk†‡	2/31	(6.5)	0.25	4/48		(8.3)	0.57	3/23	(13.0)	0.51
High risk†	2/20	(10.0)	0.13	2/34		(5.9)	0.66	1/19	(5.3)	0.17
High risk‡	0/11	(0.0)	1.00	2/14		(14.3)	0.18	2/4	(50.0)	0.21
BRCA1/2†	1/24	(4.2)	0.51	1/11		(9.1)	0.44
Sporadic‡	6/97	(6.2)	0.21	18/132		(13.6)	0.02	10/63	(15.9)	0.35

Controls	7/259	(2.7)		4/91		(4.4)		43/202	(21.3)