Risk factors and natural history of breast cancer in younger Chinese women

Table 3 Differences in the pathological characteristics of patients with invasive breast tumours (n = 5523)

	< 40 yr (n = 706) n(%)	≥40 yr (n = 4 817) n(%)	P value
Method of detection
Self-detected	589 (94.1)	3962 (90.3)	χ2 = 9.513, bP = 0.001
Screen-detected1	37 (5.9)	427 (9.7)
Presenting symptoms (for self-detected cancers)
Lump	553 (93.9)	3729 (94.1)	χ2 = 0.049, P = 0.780
Pain	29 (4.9)	173 (4.4)	χ2 = 0.375, P = 0.521
Nipple discharge	30 (5.1)	118 (3)	χ2 = 7.291, aP = 0.012
Nipple retraction	5 (0.8)	75 (1.9)	χ2 = 3.237, P = 0.090
Skin change	3 (0.5)	37 (0.9)	χ2 = 1.061, P = 0.475
Axillary node	5 (0.8)	23 (0.6)	NA2
Asymmetry	2 (0.3)	11 (0.3)	NA2
Duration of onset of symptoms (for self-detected cancers)
< 1 mo	93 (39.9)	536 (39.6)	χ2 = 0.466, P = 0.926
1-3 mo	90 (38.6)	515 (38.1)
4-12 mo	33 (14.2)	212 (15.7)
> 12 mo	17 (7.3)	89 (6.6)
Cancer stage
Early stage (Stage I-IIB)	603 (88.2)	3900(83)	χ2 = 11.490, bP = 0.001
Advanced stage (Stage IIIA –IV)	81 (11.8)	797(17)
Tumour size4
Mean ± SD (cm)	2.15 ± 1.30	2.24 ± 1.49	T = -1.514, P = 0.130
Median (cm)3	1.9	2	P = 0.065
IQR (cm)	1.40-2.70	1.40-2.80	--
≤ 2.0	361 (55.4)	2283 (51.5)	χ2 = 3.407, P = 0.071
> 2.0	291 (44.6)	2150 (48.5)
Bloom and Richardson grade4
1	80 (12.9)	806 (19.2)	χ2 = 24.682, bP < 0.001
2	258 (41.5)	1865 (44.3)
3	284 (45.7)	1537 (36.5)
Lymphovascular invasion4	229 (39.6)	1336 (33.2)	χ2 = 8.972, bP = 0.003
Disease4
Multifocality	104 (15.7)	463 (10.3)	χ2 = 17.472, bP < 0.001
Multicentricity	21 (3.2)	120 (2.7)	χ2 = 0.597, P = 0.442
Estrogen receptor + ve (ER+)4	481 (75)	3389 (75.6)	χ2 = 0.100, P = 0.768
Progesterone receptor +ve (PR+)4	400 (62.7)	2836 (63.5)	χ2 = 0.162, P = 0.693
Human Epidermal Growth Factor Receptor 2 +ve (HER2+)4	151 (28.5)	970 (26.8)	χ2 = 0.728, P = 0.402
Triple negative subtype4	74 (14.0)	450 (12.5)	χ2 = 1.000, P = 0.327
Nodal status (no. of positive nodes)4
0	409 (61.9)	2680 (59.4)	χ2 = 6.908, P = 0.075
1-3	184 (27.8)	1198 (26.6)
4-9	44 (6.7)	420 (9.3)
10+	24 (3.6)	212 (4.7)

¹Screen-detected includes monthly self-exam, clinical breast exam (routine checkups), mammography or ultrasound screening;

²Chi-square test was not available due to the small number of patients;

³Mann-Whitney U test was used;

⁴227 patients underwent neoadjuvant therapy and did not have pathology reports, thus had missing values for these parameters: tumour size, Bloom and Richardson grade, presence of lymphovascular invasion, multifocality, multicentricity, endocrine receptor status, human epidermal growth factor receptor 2 status, and nodal status.