Table 1 Clinicopathologic and US features of the training and validation cohorts

Age(years)

0.430

  ≤ 50

410 (46.9%)

88 (43.8%)

  > 50

465 (53.1%)

113 (56.2%)

Histologic types

0.676

 Ductal

812 (92.8%)

185 (92.0%)

 Lobular

21 (2.4%)

7 (3.5%)

 Others

42 (4.8%)

9 (4.5%)

Histologic grades

0.104

 I

43 (4.9%)

5 (2.5%)

 II

393 (44.9%)

81 (40.3%)

 III

439 (50.2%)

115 (57.2%)

Molecular subtypes

0.005

 Luminal A

182 (20.8%)

33 (16.4%)

 Luminal B

374 (42.7%)

70 (34.8%)

 Luminal B HER2( +)

82 (9.4%)

19 (9.5%)

 HER2-enriched

129 (14.7%)

50 (24.9%)

 Triple negative

108 (12.3%)

29 (14.4%)

Multifocality

0.096

 Unifocal

724 (82.7%)

176 (87.6%)

 Multifocality

151 (17.3%)

25 (12.4%)

Tumor location

0.436

 Upper outer quadrant

518 (59.2%)

125 (62.2%)

 Others

357 (40.8%)

76 (37.8%)

Maximum diameter

0.058

  ≤ 2 cm

328 (37.5%)

61 (30.3%)

  > 2 cm

547 (62.5%)

140 (69.7%)

Shape

1.000*

 Irregular

864 (98.7%)

199 (99.0%)

 Oval and round

11 (1.3%)

2 (1.0%)

Orientation

0.270

 Parallel

744 (85.0%)

177 (88.1%)

 Not parallel

131 (15.0%)

24 (11.9%)

Angular margin

0.109

 Yes

633 (72.3%)

134 (66.7%)

 No

242 (27.7%)

67 (33.3%)

Spiculated margin

0.221

 Yes

260 (29.7%)

51 (25.4%)

 No

615 (70.3%)

150 (74.6%)

Distance from the skin

0.342

  < 3 mm

174 (19.9%)

46 (22.9%)

  ≥ 3 mm

701 (80.4%)

155 (77.1%)