Table 2. Analysis of the histological findings in training set in US 4A patients.

Characteristics	Benign			Malignant			Total		P
	N	%		N	%		N	%
N	376			42			418
Age									0.569
≤35	48	12.8		3	7.1		51	12.2
36–50	255	67.8		30	71.4		285	68.2
>50	73	19.4		9	21.4		82	19.6
Family history of breast cancer									0.001
Yes	17	4.5		8	19.0		25	6.0
No	359	95.5		34	81.0		393	94.0
History of benign breast biopsy									0.841
No	365	97.1		41	97.6		406	97.1
Yes	11	2.9		1	2.4		12	2.9
Physical examinations									0.268
Breast pain	151	40.24		16	38.1		167	40.0
Nipple discharge	33	8.8		7	16.7		40	9.6
Palpable breast lesions	164	43.6		14	33.3		178	42.6
Others	28	7.4		5	11.9		33	7.9
U_Lesion size (mm)									0.169
<20	282	75.8		35	85.4		317	76.8
≥20	90	24.2		6	14.6		96	23.2
U_Margin									<0.001
Circumscribed	229	60.9		8	19.0		237	56.7
Not circumscribed	147	39.1		34	81.0		181	43.3
U_Shape									<0.001
Oval	212	56.4		9	21.4		221	52.9
Round	40	10.6		7	16.7		47	11.2
Irregular	124	33.0		26	61.9		150	35.9
U_ Orientation									<0.001
Parallel	290	77.1		20	47.6		310	74.2
Not parallel	86	22.9		22	52.4		108	25.8
U_Lymph_nodes									0.009
Low suspicious	3	0.8		3	7.1		6	1.4
No/normal	373	99.2		39	92.9		412	98.6
U_Internal vascularity									0.145
Yes	95	25.3		15	35.7		110	26.3
No	281	74.7		27	64.3		308	73.7
U_Echo pattern									0.381
Homogenous	313	83.5		32	78.0		345	82.9
Heterogeneous	62	16.5		9	22.0		71	17.1
U_Posterior features									0.442
No shadowing	357	94.9		41	97.6		398	95.2
Shadowing	19	5.1		1	2.4		20	4.8
U_Calcifications									0.325
No	332	88.5		35	83.3		367	88.0
Yes	43	11.5		7	16.7		50	12.0
U_Multiple solid lesions									0.345
No	234	62.2		23	54.8		257	61.5
Yes	142	37.8		19	45.2		161	38.5
M_density of mass									0.545
Equal density	296	78.7		30	71.5		326	78.0
High density	80	21.3		12	28.6		92	22.0
BI-RADS_M									0.182
1–3	278	73.9		27	64.3		305	73.0
4 and above	98	26.1		15	35.7		113	27.0
M_Calcifications									<0.001
No/normal	368	97.9		33	78.6		401	95.9
Suspicious	8	2.1		9	21.4		17	4.1
Location of suspicious calcifications									0.620
In the mass	5	62.5		7	77.8		12	70.6
Outside the mass	3	37.5		2	22.2		5	29.4
M_Architectural distortion									0.996
No	367	97.6		41	97.6		408	97.6
Yes	9	2.4		1	2.4		10	2.4
M_Asymmetry									0.903
No	351	93.4		39	92.9		390	93.3
Yes	25	6.6		3	7.1		28	6.7

U, ultrasonography; M, mammography; BI-RADS, Breast Imaging Reporting and Data System.