Table 2 Baseline demographic characteristics of all young patients according to various molecular subtypes (n = 1099)

BC family history

0.023

 YES

62 (10.4)

16 (13.3)

5 (6.7)

21 (10.4)

9 (8.3)

 NO

524 (88.2)

104 (86.7)

68 (90.7)

179 (89.1)

94 (86.2)

 Unknown

8 (1.3)

0 (0)

2 (2.7)

1 (0.5)

6 (5.5)

Reproductive history

0.003

 YES

451 (75.9)

92 (76.7)

61 (81.3)

146 (72.6)

77 (70.6)

 NO

136 (22.9)

28 (23.3)

12 (16.0)

55 (27.4)

26 (23.9)

 Unknown

7 (1.2)

0 (0)

2 (2.7)

0 (0)

6 (5.5)

Breastfeeding history

< 0.001

 YES

410 (69.0)

79 (65.8)

59 (78.7)

128 (63.7)

69 (63.3)

 NO

177 (29.8)

41 (34.2)

14 (18.7)

72 (35.8)

33 (30.3)

 Unknown

7 (1.2)

0 (0)

2 (2.7)

1 (0.5)

7 (6.4)

Tumor size

0.007

 T1

250 (42.1)

39 (32.5)

17 (22.7)

69 (34.3)

45 (41.3)

 T2

261 (43.9)

61 (50.8)

40 (53.3)

103 (51.2)

43 (39.4)

 T3

45 (7.6)

10 (8.3)

8 (10.7)

12 (6.0)

13 (11.9)

 T4

3 (0.5)

5 (4.2)

3 (4.0)

4 (2.0)

1 (0.9)

 Tx

35 (5.9)

5 (4.2)

7 (9.3)

13 (6.5)

7 (6.4)

Stage

< 0.001

 I

166 (27.9)

27 (22.5)

8 (10.7)

48 (23.9)

33 (30.3)

 II a

199 (33.5)

40 (33.3)

26 (34.7)

90 (44.8)

28 (25.7)

 II b

85 (14.3)

16 (13.3)

13 (17.3)

28 (13.9)

17 (15.6)

 III a

72 (12.1)

15 (12.5)

12 (16.0)

17 (8.5)

10 (9.2)

 III b

2 (0.3)

1 (0.8)

2 (2.7)

3 (1.5)

0 (0)

 III c

48 (8.1)

17 (14.2)

12 (6.0)

4 (2.0)

16 (14.7)

 Unknown

22 (3.7)

4 (3.3)

2 (2.7)

11 (5.5)

5 (4.6)

LN metastasis

< 0.001

 N0

312 (52.5)

55 (45.8)

36 (48.0)

134 (66.7)

48 (44.0)

 N1

161 (27.1)

30 (25.0)

14 (18.7)

46 (22.9)

25 (22.9)

 N2

70 (11.8)

16 (13.3)

13 (17.2)

16 (8.0)

9 (8.3)

 N3

46 (7.7)

17 (14.2)

12 (16.0)

2 (1.0)

17 (15.6)

 Unknown

5 (0.8)

2 (1.7)

0 (0)

3 (1.5)

10 (9.2)

Histological grade

< 0.001

 Well

29 (4.9)

0 (0)

1 (1.3)

2 (1.0)

3 (2.8)

 Moderately

371 (62.5)

67 (55.8)

36 (48.0)

78 (38.8)

42 (38.5)

 Poorly

50 (8.4)

25 (20.8)

16 (21.3)

52 (25.9)

20 (18.3)

 Unknown

144 (24.2)

28 (23.3)

22 (29.3)

69 (34.3)

44 (40.4)

Pathological type

0.906

 IDC

534 (89.9)

110 (91.7)

71 (94.7)

183 (91.0)

101 (92.7)

 IBC

7 (1.2)

1 (0.8)

0 (0)

1 (0.5)

1 (0.9)

 Others

53 (8.9)

9 (7.5)

4 ( (5.3)

17 (8.5)

7 (6.4)

Final surgery

0.002

 BCS

143 (24.1)

19 (15.8)

14 (18.7)

64 (31.8)

17 (15.6)

 Mastectomy

451 (75.9)

101 (84.2)

61 (81.3)

137 (68.2)

92 (84.4)

NACT

0.003

 YES

80 (13.5)

19 (15.8)

23 (30.7)

33 (16.4)

21 (19.3)

 NO

514 (86.5)

101 (84.2)

52 (69.3)

168 (83.6)

88 (80.7)

ACT

0.046

 A-based

72 (12.1)

17 (14.2)

12 (16.0)

24 (11.9)

15 (13.8)

 A- and T-based

490 ( (82.5)

97 (80.8)

58 (77.3)

162 (80.6)

77 (70.6)

 Unknown

28 (4.7)

6 (5.0)

5 (6.7)

12 (6.0)

16 (14.7)

 None

4 (0.7)

0 (0)

0 (0)

3 (1.5)

1 (0.9)

Radiotherapy

< 0.001

 YES

304 (51.2)

59 (49.2)

46 (61.3)

105 (52.2)

43 (39.4)

 NO

254 (42.8)

52 (43.3)

24 (32.0)

85 (42.3)

38 (34.9)

 Unknown

36 (6.1)

9 (7.5)

5 (6.7)

11 (5.5)

28 (25.7)

ET

< 0.001

 YES

467 (78.6)

89 (74.2)

0 (0)

0 (0)

33 (30.3)

 NO

27 (4.5)

8 (6.7)

70 (93.3)

194 (96.5)

17 (15.6)

 Unknown

100 (16.8)

23 (19.2)

5 (6.7)

7 (3.5)

59 (54.1)

OFS

< 0.001

 YES

147 (24.7)

34 (28.3)

0 (0)

0 (0)

6 (5.5)

 NO

215 (36.2)

46 (38.3)

67 (89.3)

189 (94.0)

28 (25.7)

 Unknown

232 (39.1)

40 (33.3)

8 (10.7)

12 (6.0)

75 (68.8)

TT

< 0.001

 YES

2 (0.3)

51 (42.5)

32 (42.7)

0 (0)

0 (0)

 NO

553 (93.1)

41 (34.2)

23 (30.7)

195 (97.0)

24 (22.0)

 Unknown

39 (6.6)

28 (23.3)

20 (26.7)

6 (3.0)

85 (78.0)