Table 1.
Malignancy frequency distributions, clinical and US features of patients in the training and external validation sets
| Features | Training set, (n = 1027) | Validation set, (n = 120) | p value |
|---|---|---|---|
| Malignancy frequency | 442 | 51 | 0.910 |
| Sex | 0.781 | ||
| Male | 493 | 56 | |
| Female | 534 | 64 | |
| Age (year) | 0.592 | ||
| ≤ 45 | 337 | 36 | |
| 45–60 | 344 | 38 | |
| ≥ 60 | 346 | 46 | |
| Pain | 0.731 | ||
| Absent | 709 | 81 | |
| Present | 318 | 39 | |
| Duration (month) | 0.070 | ||
| ≥ 12 | 290 | 46 | |
| 1–12 | 430 | 44 | |
| ≤ 1 | 307 | 30 | |
| History of malignancy | 0.863 | ||
| Absent | 803 | 93 | |
| Present | 224 | 27 | |
| Location | 0.741 | ||
| Head or neck | 146 | 14 | |
| Trunk or hip | 360 | 44 | |
| Limbs | 521 | 62 | |
| Layer | 0.247 | ||
| Superficial | 336 | 33 | |
| Deep | 691 | 87 | |
| Size (cm) | 0.649 | ||
| ≤ 2 | 189 | 24 | |
| 2–5 | 425 | 53 | |
| ≥ 5 | 413 | 43 | |
| Shape | 0.895 | ||
| Regular | 597 | 69 | |
| Irregular | 430 | 51 | |
| Margin | 0.837 | ||
| Well-defined | 675 | 80 | |
| Ill-Defined | 352 | 40 | |
| Echogenicity | 0.090 | ||
| Predominantly isoechoic | 104 | 5 | |
| Predominantly hyperechoic | 141 | 20 | |
| Predominantly hypoechoic | 782 | 95 | |
| Composition | 0.236 | ||
| Predominantly cystic | 6 | 2 | |
| Mixed | 79 | 6 | |
| Predominantly solid | 942 | 112 | |
| Calcification | 0.896 | ||
| Absent | 964 | 113 | |
| Present | 63 | 7 | |
| Bone invasion | 0.708 | ||
| Absent | 967 | 114 | |
| Present | 60 | 6 | |
| Vascularity | 0.044* | ||
| Grade 0 | 338 | 40 | |
| Grade I | 168 | 30 | |
| Grade II | 228 | 27 | |
| Grade III | 293 | 23 |
n number, US ultrasonography
* Indicates a significant difference between the two sets