Table 2.

Marker expression of benign tissue in breast cancer cases by parity

Immunohistochemical markera		Parity				Ptrendb
		All	0	1–2	≥ 3
ERα	Total N	157	22	61	74	0.02
	N, positive	35	10	11	14
	%, positive	22.3	45.5	18.0	18.9
ERβ	Total N	157	22	62	73	0.37
	N, positive	47	6	17	24
	%, positive	29.9	27.3	27.4	32.9
PR	Total N	158	23	61	74	0.75
	N, positive	81	12	32	37
	%, positive	51.3	52.2	52.5	50.0
Her2/neu	Total N	156	22	61	73	0.90
	N, positive	52	8	21	23
	%, positive	33.3	36.4	34.4	31.5
Ki-67	Total N	155	22	60	73	0.61
	N, positive	90	15	30	45
	%, positive	58.1	68.2	50.0	61.6
PCNA	Total N	158	23	61	74	0.04
	N, positive	63	13	27	23
	%, positive	39.9	56.5	44.3	31.1

^aERα = estrogen receptor alpha; ERβ = estrogen receptor beta; PR = progesterone receptor; HER2/neu = human epidermal growth factor receptor 2; PCNA = proliferating cell nuclear antigen. Positive marker expression is defined as <10% vs. ≥10% epithelial staining for ERα, ERβ, Her2/neu, and PCNA and as no vs. any epithelial staining for PR and Ki-67.

^bP_trend value from logistic regression analysis using parity categories (0, 1–2, and ≥3) as a continuous variable adjusted for age at diagnosis (continuous) and body mass index (continuous).