J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website https://jocmr.elmerjournals.com

Original Article

Volume 000, Number 000, January 2026, pages 000-000

Predicting Breast Imaging-Reporting and Data System Classification of Palpable Breast Masses Using Ultrasound to Prioritize Mammography Queues

Figure 2. Receiver operating characteristic (ROC) curve of step 1 model for differentiating BI-RADS 3–5 from BI-RADS 1–2. AuROC: area under the receiver operating characteristic curve; CI: confidence interval.

Figure 3. Receiver operating characteristic (ROC) curve of step 2 model for differentiating BI-RADS 4–5 from BI-RADS 3. AuROC: area under the receiver operating characteristic curve; CI: confidence interval.

Figure 4. Risk curve showing the probability of BI-RADS 3–5 with BI-RADS 1–2 as baseline and the cutoff point of the linear combination. BI-RADS: Breast Imaging Reporting and Data System.

Figure 5. Risk curve showing the probability of BI-RADS 4–5 with BI-RADS 3 as baseline and the cutoff point of the linear combination. BI-RADS: Breast Imaging Reporting and Data System.

**Table 1.** Scheme of Reference and Predicted BI-RADS Classifications With Likelihood of Malignancy and Management, Modified From the ACR BI-RADS Fifth Edition (2013)
Reference classification (ACR BI-RADS fifth edition)	Likelihood of cancer	Management	Predicted classification	Chance of malignancy
ACR: American College of Radiology; BI-RADS: Breast Imaging Reporting and Data System.
BI-RADS 1 (negative); BI-RADS 2 (benign)	Essentially 0%	Routine screening	Predicted BI-RADS 1–2	Low
BI-RADS 3 (probably benign)	> 0% but ≤ 2%	Short-interval follow-up (6 months)	Predicted BI-RADS 3	Medium
BI-RADS 4 (suspicious)	> 2% to < 95%	Tissue diagnosis	Predicted BI-RADS 4–5	High
BI-RADS 5 (highly suggestive of malignancy)	≥ 95%

Table 1. Scheme of Reference and Predicted BI-RADS Classifications With Likelihood of Malignancy and Management, Modified From the ACR BI-RADS Fifth Edition (2013)

Reference classification (ACR BI-RADS fifth edition)

Likelihood of cancer

Management

Predicted classification

Chance of malignancy

ACR: American College of Radiology; BI-RADS: Breast Imaging Reporting and Data System.

BI-RADS 1 (negative); BI-RADS 2 (benign)

Essentially 0%

Routine screening

Predicted BI-RADS 1–2

Low

BI-RADS 3 (probably benign)

> 0% but ≤ 2%

Short-interval follow-up (6 months)

Predicted BI-RADS 3

Medium

BI-RADS 4 (suspicious)

> 2% to < 95%

Tissue diagnosis

Predicted BI-RADS 4–5

High

BI-RADS 5 (highly suggestive of malignancy)

≥ 95%

**Table 2.** Baseline Characteristics and Ultrasound Findings Across BI-RADS Categories
Variables	BI-RADS 1–2 (n = 142), n (%)	BI-RADS 3 (n = 50), n (%)	BI-RADS 4–5 (n = 198), n (%)	P value
BI-RADS: Breast Imaging Reporting and Data System; SD: standard deviation; None: no mass.
Age (years), mean ± SD	49.7 ± 9.6	50.4 ± 11.1	58.7 ± 12.8	0.001
Ultrasound findings
Shape
None	28 (19.7)	0 (0)	0 (0)	< 0.001
Oval	111 (78.2)	47 (94.0)	46 (23.2)
Round	1 (0.7)	2 (4.0)	9 (4.5)
Irregular	2 (1.4)	1 (2.0)	143 (72.2)
Margin
None	28 (19.7)	0 (0)	0 (0)	< 0.001
Circumscribed	114 (80.3)	48 (96.0)	40 (20.2)
Angular	0 (0)	0 (0)	19 (9.6)
Microlobulated	0 (0)	0 (0)	27 (14.1)
Indistinct	0 (0)	2 (4.0)	62 (31.3)
Spiculated	0 (0)	0 (0)	50 (25.3)
Orientation
None	28 (19.7)	0 (0)	0 (0)	< 0.001
Parallel	114 (80.1)	49 (98.0)	120 (60.6)
Not parallel	0 (0)	1 (2.0)	78 (39.4)
Echo pattern
None	28 (19.7)	0 (0)	0 (0)	< 0.001
Anechoic	104 (73.2)	8 (16.0)	0 (0)
Hyperechoic	0 (0)	2 (4.0)	0 (0)
Hypoechoic	10 (7.0)	37 (74.0)	114 (57.6)
Isoechoic	0 (0)	2 (4.0)	1 (0.5)
Heterogeneous	0 (0)	1 (2.0)	67 (33.8)
Complex cystic-solid	0 (0)	0 (0)	16 (8.1)
Posterior features
None	28 (19.7)	0 (0)	0 (0)	< 0.001
No posterior features	28 (19.7)	43 (86.0)	94 (47.5)
Enhancement	86 (61.6)	7 (14.0)	78 (49.4)
Shadowing	0 (0)	0 (0)	25 (12.6)
Combined pattern	0 (0)	0 (0)	1 (0.5)
Calcifications
None	28 (19.7)	0 (0)	0 (0)	< 0.001
No calcifications	114 (80.3)	50 (100)	117 (59.1)
Calcifications in a mass	0 (0)	0 (0)	80 (40.4)
Intraductal calcifications	0 (0)	0 (0)	1 (0.5)
Axillary lymph nodes
None	35 (13.0)	0 (0)	0 (0)	< 0.001
Normal	106 (36.7)	48 (16.6)	135 (46.7)
Abnormal	0 (0)	0 (0)	57 (28.7)

Table 2. Baseline Characteristics and Ultrasound Findings Across BI-RADS Categories

Variables

BI-RADS 1–2 (n = 142), n (%)

BI-RADS 3 (n = 50), n (%)

BI-RADS 4–5 (n = 198), n (%)

P value

BI-RADS: Breast Imaging Reporting and Data System; SD: standard deviation; None: no mass.

Age (years), mean ± SD

49.7 ± 9.6

50.4 ± 11.1

58.7 ± 12.8

0.001

Ultrasound findings

Shape

None

28 (19.7)

0 (0)

< 0.001

Oval

111 (78.2)

47 (94.0)

46 (23.2)

Round

1 (0.7)

2 (4.0)

9 (4.5)

Irregular

2 (1.4)

1 (2.0)

143 (72.2)

Margin

None

28 (19.7)

0 (0)

< 0.001

Circumscribed

114 (80.3)

48 (96.0)

40 (20.2)

Angular

0 (0)

19 (9.6)

Microlobulated

0 (0)

27 (14.1)

Indistinct

0 (0)

2 (4.0)

62 (31.3)

Spiculated

0 (0)

50 (25.3)

Orientation

None

28 (19.7)

0 (0)

< 0.001

Parallel

114 (80.1)

49 (98.0)

120 (60.6)

Not parallel

0 (0)

1 (2.0)

78 (39.4)

Echo pattern

None

28 (19.7)

0 (0)

< 0.001

Anechoic

104 (73.2)

8 (16.0)

0 (0)

Hyperechoic

0 (0)

2 (4.0)

0 (0)

Hypoechoic

10 (7.0)

37 (74.0)

114 (57.6)

Isoechoic

0 (0)

2 (4.0)

1 (0.5)

Heterogeneous

0 (0)

1 (2.0)

67 (33.8)

Complex cystic-solid

0 (0)

16 (8.1)

Posterior features

None

28 (19.7)

0 (0)

< 0.001

No posterior features

28 (19.7)

43 (86.0)

94 (47.5)

Enhancement

86 (61.6)

7 (14.0)

78 (49.4)

Shadowing

0 (0)

25 (12.6)

Combined pattern

0 (0)

1 (0.5)

Calcifications

None

28 (19.7)

0 (0)

< 0.001

No calcifications

114 (80.3)

50 (100)

117 (59.1)

Calcifications in a mass

0 (0)

80 (40.4)

Intraductal calcifications

0 (0)

1 (0.5)

Axillary lymph nodes

None

35 (13.0)

0 (0)

< 0.001

Normal

106 (36.7)

48 (16.6)

135 (46.7)

Abnormal

0 (0)

57 (28.7)

**Table 3.** Step 1: Multivariable Risk Difference Regression With the stepwise Method of Ultrasound Predictors for Predicted BI-RADS 3–5 Versus BI-RADS 1–2 (Baseline)
Predictors	Risk difference	95% CI	P value
BI-RADS: Breast Imaging Reporting and Data System; CI: confidence interval; None: no mass.
Shape
None	Baseline	Baseline	Baseline
Oval	1.06	0.89, 1.24	< 0.001
Round	1.30	1.05, 1.54	< 0.001
Irregular	1.08	0.94, 1.23	< 0.001
Margin
None	Baseline	Baseline	Baseline
Circumscribed	−0.11	−0.22, 0.01	0.069
Angular	−0.00	−0.11, 0.11	0.980
Microlobulated	−0.01	−0.11, 0.09	0.840
Indistinct	−0.01	−0.09, 0.07	0.801
Echo pattern
None	Baseline	Baseline	Baseline
Anechoic	−0.89	−1.00, −0.78	< 0.001
Hyperechoic	−0.07	−0.39, 0.24	0.651
Hypoechoic	−0.10	−0.20, 0.01	0.081
Isoechoic	−0.03	−0.28, 0.23	0.833
Heterogeneous	−0.06	−0.17, 0.06	0.329

Table 3. Step 1: Multivariable Risk Difference Regression With the stepwise Method of Ultrasound Predictors for Predicted BI-RADS 3–5 Versus BI-RADS 1–2 (Baseline)

Predictors

Risk difference

95% CI

P value

BI-RADS: Breast Imaging Reporting and Data System; CI: confidence interval; None: no mass.

Shape

None

Baseline

Oval

1.06

0.89, 1.24

< 0.001

Round

1.30

1.05, 1.54

< 0.001

Irregular

1.08

0.94, 1.23

< 0.001

Margin

None

Baseline

Circumscribed

−0.11

−0.22, 0.01

0.069

Angular

−0.00

−0.11, 0.11

0.980

Microlobulated

−0.01

−0.11, 0.09

0.840

Indistinct

−0.01

−0.09, 0.07

0.801

Echo pattern

None

Baseline

Anechoic

−0.89

−1.00, −0.78

< 0.001

Hyperechoic

−0.07

−0.39, 0.24

0.651

Hypoechoic

−0.10

−0.20, 0.01

0.081

Isoechoic

−0.03

−0.28, 0.23

0.833

Heterogeneous

−0.06

−0.17, 0.06

0.329

**Table 4.** Step 2: Multivariable Risk Difference Regression Using the Stepwise Method of Ultrasound Predictors for Predicted BI-RADS 4–5 Versus BI-RADS 3 (Baseline)
Predictors	Risk difference	95% CI	P value
BI-RADS: Breast Imaging Reporting and Data System; CI: confidence interval; None: no mass.
Shape
None	Baseline	Baseline	Baseline
Round	0.50	0.21, 0.79	0.001
Irregular	0.15	0.01, 0.28	0.030
Margin
None	Baseline	Baseline	Baseline
Angular	0.40	0.22, 0.57	< 0.001
Microlobulated	0.36	0.19, 0.53	< 0.001
Indistinct	0.35	0.21, 0.49	< 0.001
Spiculated	0.39	0.23, 0.55	< 0.001
Echo pattern
None	Baseline	Baseline	Baseline
Hypoechoic	0.67	0.26, 1.07	0.001
Isoechoic	0.30	−0.21, 0.81	0.249
Heterogeneous	0.81	0.40, 1.22	< 0.001
Complex cystic-solid	1.06	0.64, 1.49	< 0.001

Table 4. Step 2: Multivariable Risk Difference Regression Using the Stepwise Method of Ultrasound Predictors for Predicted BI-RADS 4–5 Versus BI-RADS 3 (Baseline)

Predictors

Risk difference

95% CI

P value

BI-RADS: Breast Imaging Reporting and Data System; CI: confidence interval; None: no mass.

Shape

None

Baseline

Round

0.50

0.21, 0.79

0.001

Irregular

0.15

0.01, 0.28

0.030

Margin

None

Baseline

Angular

0.40

0.22, 0.57

< 0.001

Microlobulated

0.36

0.19, 0.53

< 0.001

Indistinct

0.35

0.21, 0.49

< 0.001

Spiculated

0.39

0.23, 0.55

< 0.001

Echo pattern

None

Baseline

Hypoechoic

0.67

0.26, 1.07

0.001

Isoechoic

0.30

−0.21, 0.81

0.249

Heterogeneous

0.81

0.40, 1.22

< 0.001

Complex cystic-solid

1.06

0.64, 1.49

< 0.001

**Table 5.** Apparent and Bootstrap Performance of Step 1 and Step 2 Prediction Models
Process	Parameters	Apparent performance	Bootstrap performance
AuROC: area under the receiver operating characteristic curve; CITL: calibration-in-the-large; E:O ratio: expected-to-observed outcomes ratio; NA: not applicable.
Step 1	AuROC	0.9801 (0.9696, 0.9907)	0.9800 (0.9710, 0.9910)
	Slope	1.0000 (0.8390, 1.1610)	0.9800 (0.8230, 1.1450)
	E:O ratio	1.0000	1.0010 (0.9720, 1.0410)
	CITL	−0.0000 (−0.4850, 0.4850)	−0.0240 (−0.6580, 0.5700)
	Bootstrap shrinkage	NA	0.9800
Step 2	AuROC	0.9623 (0.9411, 0.9835)	0.9630 (0.9420, 0.9900)
	Slope	1.0000 (0.7110, 1.2890)	0.8960 (0.0000, 1.2830)
	E:O ratio	1.0000	0.9190 (0.2500, 1.0240)
	CITL	0.0000 (−0.5810, 0.5810)	0.0700 (−0.4270, 0.8750)
	Bootstrap shrinkage	NA	0.8960

Table 5. Apparent and Bootstrap Performance of Step 1 and Step 2 Prediction Models

Process

Parameters

Apparent performance

Bootstrap performance

AuROC: area under the receiver operating characteristic curve; CITL: calibration-in-the-large; E:O ratio: expected-to-observed outcomes ratio; NA: not applicable.

Step 1

AuROC

0.9801 (0.9696, 0.9907)

0.9800 (0.9710, 0.9910)

Slope

1.0000 (0.8390, 1.1610)

0.9800 (0.8230, 1.1450)

E:O ratio

1.0000

1.0010 (0.9720, 1.0410)

CITL

−0.0000 (−0.4850, 0.4850)

−0.0240 (−0.6580, 0.5700)

Bootstrap shrinkage

0.9800

Step 2

AuROC

0.9623 (0.9411, 0.9835)

0.9630 (0.9420, 0.9900)

Slope

1.0000 (0.7110, 1.2890)

0.8960 (0.0000, 1.2830)

E:O ratio

1.0000

0.9190 (0.2500, 1.0240)

CITL

0.0000 (−0.5810, 0.5810)

0.0700 (−0.4270, 0.8750)

Bootstrap shrinkage

0.8960

**Table 6.** Confusion Matrix of Predicted Versus Reference BI-RADS Classifications
Predicted classification	Reference classification	Total
BI-RADS: Breast Imaging Reporting and Data System.
Predicted BI-RADS 1–2	132 (33.9%)	8 (2.0%)	0 (0%)	140 (35.9%)
Predicted BI-RADS 3	10 (2.5%)	41 (10.5%)	26 (6.7%)	77 (19.7%)
Predicted BI-RADS 4–5	0 (0%)	1 (0.3%)	172 (44.1%)	173 (44.4%)
Total	142 (36.4%)	50 (12.8%)	198 (50.8%)	390 (100%)

Table 6. Confusion Matrix of Predicted Versus Reference BI-RADS Classifications

Predicted classification

Reference classification

Total

BI-RADS 1–2 (n = 142)

BI-RADS 3 (n = 50)

BI-RADS 4–5 (n = 198)

BI-RADS: Breast Imaging Reporting and Data System.

Predicted BI-RADS 1–2

132 (33.9%)

8 (2.0%)

0 (0%)

140 (35.9%)

Predicted BI-RADS 3

10 (2.5%)

41 (10.5%)

26 (6.7%)

77 (19.7%)

Predicted BI-RADS 4–5

0 (0%)

1 (0.3%)

172 (44.1%)

173 (44.4%)

Total

142 (36.4%)

50 (12.8%)

198 (50.8%)

390 (100%)

**Table 7.** Sensitivity Analysis of Discriminative Ability by Method (Addressing Incorporation Bias)
Process	Method	Patients (n)	AuROC	95% CI
AuROC: area under the receiver operating characteristic curve; CI: confidence interval.
Step 1	Overall model	390	0.9801	0.9695, 0.9907
	Mammography-based interpretation alone	172	0.9945	0.9866, 1.0000
Step 2	Overall model	240	0.9623	0.9411, 0.9835
	Mammography-based interpretation alone	163	0.9876	0.9707, 1.0000

Table 7. Sensitivity Analysis of Discriminative Ability by Method (Addressing Incorporation Bias)

Process

Method

Patients (n)

AuROC

95% CI

AuROC: area under the receiver operating characteristic curve; CI: confidence interval.

Step 1

Overall model

390

0.9801

0.9695, 0.9907

Mammography-based interpretation alone

172

0.9945

0.9866, 1.0000

Step 2

Overall model

240

0.9623

0.9411, 0.9835

Mammography-based interpretation alone

163

0.9876

0.9707, 1.0000

**Table 8.** Model-Based Scheduling Scheme: A New Strategy for Mammography Queue Management
Process	Linear combination	Predicted group	Chance of malignancy	Queue	Waiting time
BI-RADS: Breast Imaging Reporting and Data System.
Step 1	< 0.625	BI-RADS 1–2	Low	Normal	Standard queue
	≥ 0.625	BI-RADS 3–5	Proceed to step 2 evaluation
Step 2	< 0.610	BI-RADS 3	Medium	Semi-urgent	Within 4 - 8 weeks
	≥ 0.610	BI-RADS 4–5	High	Urgent	Within 4 weeks

Table 8. Model-Based Scheduling Scheme: A New Strategy for Mammography Queue Management

Process

Linear combination

Predicted group

Chance of malignancy

Queue

Waiting time

BI-RADS: Breast Imaging Reporting and Data System.

Step 1

< 0.625

BI-RADS 1–2

Low

Normal

Standard queue

≥ 0.625

BI-RADS 3–5

Proceed to step 2 evaluation

Step 2

< 0.610

BI-RADS 3

Medium

Semi-urgent

Within 4 - 8 weeks

≥ 0.610

BI-RADS 4–5

High

Urgent

Within 4 weeks