Table 1 Baseline and clinical characteristics among age groups*

Tumor size—cm

2.70 ± 1.44

2.72 ± 1.37

2.73 ± 1.40

Breast side—no. (%)

Left

297 (52.7)

2339 (51.8)

357 (53.3)

Right

267 (47.3)

2180 (48.2)

313 (46.7)

Pathology subtype—no. (%)

Insitu

17 (3.1)^a

129 (3)^a

16 (2.5)^a

Mucinous

2 (0.4)^a

40 (0.9)^a

14 (2.2)^b

Medullary

25 (4.6)^a

172 (4)^a

17 (2.7)^a

Papillary

2 (0.4)^b

8 (0.2)^b

6 (0.9)^a

Invasive ductal

448 (82.4)^b

3650 (83.8)^b

512 (80.4)^a

Invasive lobular

4 (0.7)^a

151 (3.5)^b

34 (5.3)^c

Mixed pattern

25 (4.6)^a

131 (3)^b

13 (2)^b

Other

19 (3.5)^a

72 (1.7)^b

25 (3.9)^a

Insitu component—no. (%)

Yes

138 (31.1)

1058 (31.1)

161 (34.5)

No

306 (68.9)

2339 (68.9)

305 (65.5)

Tumor necrosis—no. (%)

Yes

169 (36.4)^a

1536 (44.6)^b

232 (48.9)^b

No

295 (63.6)^a

1908 (55.4)^b

242 (51.1)^b

Invasion—no. (%)

Lymphatic

49 (9.8)^a

540 (13.7)^b

87 (14.9)^b

Vascular

5 (1)^a

80 (2)^b

16 (2.7)^b

Preneural

36 (7.2)^a

298 (7.6)^a

54 (9.3)^a

Lymphatic & preneural

7 (1.4)^a

109 (2.8)^a

25 (4.3)^b

Preneural & vascular

2 (0.4)^a

37 (0.9)^a

8 (1.4)^a

Lymphatic & vascular

108 (21.6)^a

747 (19)^a

87 (14.9)^b

None

192 (38.5)^a

1485 (37.8)^a

212 (36.4)^a

ER receptor—no. (%)

Positive

363 (68.6)^a

3162 (74.4)^b

475 (76.9)^b

Negative

165(31.2)^a

1082 (25.5)^b

143 (23.1)^b

PR receptor—no. (%)

Positive

335 (63.4)^a

2906 (68.6)^b

426 (69.7)^b

Negative

193 (36.3)^a

1324 (31.2)^b

184 (30.1)^b

HER2 receptor—no. (%)

Positive

151 (29.9%)^a

942 (27.2%)^a

84 (19.2%)^b

Negative

354 (70.1%)^a

2521 (72.8%)^a

353 (80.8%)^b

Stage—no. (%)

0

17 (3.5)^a

129 (3.3)^a

16 (3.1)^a

1

101 (20.9)^a

895 (22.9)^a

122 (23.5)^a

2

208 (43.1)^a

1824 (46.7)^a

272 (52.4)^b

3

150 (31.1)^a

1001 (25.6)^b

102 (19.7)^c

4

7 (1.4)^a

59 (1.5)^a

7 (1.3)^a

Grade—no. (%)

1

70 (15.9)^a

759 (21.9)^b

139 (28)^c

2

250 (56.7)^a

1991 (57.4)^a

275 (55.4)^a

3

121 (27.4)^a

713 (20.6)^b

82 (16.5)^c

Grade of nucleus—no. (%)

1

26 (12)^a

215 (18.3)^b

40 (29.9)^c

2

97 (44.9)^a

553 (47.2)^a

57 (42.5)^a

3

93 (43.1)^a

404 (34.5)^b

37 (27.6)^b