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Table 1 Characteristics between the training set and the validation set

From: Nomogram for predicting preoperative regional lymph nodes metastasis in patients with metaplastic breast cancer: a SEER population-based study

Characteristics All Patients
n = 2205 (%)
Training
n = 1543 (%)
Validation
n = 662 (%)
P value
Age (years)
 Median 60 59 61  
 ≤ 60 1135 (51.5) 814 (52.8) 321 (48.5) 0.066
 > 60 1070 (48.5) 729 (47.2) 341 (51.5)  
Race
 White 1691 (76.7) 1165 (75.5) 526 (79.5) 0.103
 Black 364 (16.5) 271 (17.6) 93 (14.0)  
 Othersa 150 (6.8) 107 (6.9) 43 (6.5)  
Marital status
 Unmarried 959 (43.5) 670 (43.4) 289 (43.6) 0.750
 Married 1173 (53.2) 819 (53.1) 354 (53.5)  
 Unknown 73 (3.3) 54 (3.5) 19 (2.9)  
Grade
 I 103 (4.7) 67 (4.4) 36 (5.4) 0.666
 II 299 (13.6) 207 (13.4) 92 (13.9)  
 III 1701 (77.1) 1199 (77.7) 502 (75.8)  
 IV 102 (4.6) 70 (4.5) 32 (4.9)  
Laterality
 Right 1129 (51.2) 777 (50.4) 352 (53.2) 0.225
 Left 1076 (48.8) 766 (49.6) 310 (46.8)  
ER status
 Negative 1803 (81.8) 1265 (82.0) 538 (81.3) 0.691
 Positive 402 (18.2) 278 (18.0) 124 (18.7)  
PR status
 Negative 1919 (87.0) 1342 (87.0) 577 (87.2) 0.905
 Positive 286 (13.0) 201 (13.0) 85 (12.8)  
HER-2 status
 Negative 1091 (49.5) 751 (48.7) 340 (51.4) 0.155
 Positive 76 (3.4) 60 (3.9) 16 (2.4)  
 Unknown 1038 (47.1) 732 (47.4) 306 (46.2)  
Tumor size
 ≤ 2 cm 572 (25.9) 399 (25.9) 173 (26.1) 0.976
 > 2 cm and ≤ 5 cm 1157 (52.5) 812 (52.6) 345 (52.1)  
 > 5 cm 476 (21.6) 332 (21.5) 144 (21.8)  
Regional lymph nodes
 Negative 1659 (75.2) 1164 (75.4) 495 (74.8) 0.741
 Positive 546 (24.8) 379 (24.6) 167 (25.2)  
  1. ER Estrogen receptor, PR Progesterone receptor, HER-2 Human epidermal growth factor receptor-2
  2. aIncludes: American Indian, native Alaskan and Asian, Pacific Islander