Rationale and Objectives
The aim of this study was to develop a more reliable ultrasonic elastographic diagnostic method than a five-point scoring system by analyzing the difference in stiffness between benign and malignant breast lesions.
Materials and Methods
From January 2008 to April 2009, 559 solid lesions (415 benign, 144 malignant) in 437 consecutive patients (age range, 12–77 years) were examined using ultrasound elastography (UE). Final diagnosis was made on the basis of histopathologic findings. The strain ratios of the lesions were calculated. The area under the curve and cutoff point, both of which were obtained using receiver-operating characteristic curve analysis, were used to assess diagnostic performance. Diagnostic performance was further compared to that generated using a five-point scoring system with the z test. The sensitivity, specificity, and accuracy of these two evaluation systems were compared using McNemar’s test.
Results
The strain ratios of benign lesions (mean, 1.83 ± 1.22) and malignant lesions (mean, 8.38 ± 7.65) were significantly different ( P < .00001). When a cutoff point of 3.05 was introduced, UE had 92.4% sensitivity, 91.1% specificity, and 91.4% accuracy. The area under the curve for strain ratio–based elastographic analysis was 0.944, and the area under the curve for the five-point scoring system was 0.885. The diagnostic performance of strain ratio–based elastographic analysis was better than that of the five-point scoring system with UE ( P < .05).
Conclusions
Strain ratio–based elastographic analysis can provide a new, more reliable diagnostic tool in comparison to a five-point scoring system for UE.
Biologic tissue possesses a specific inherent elasticity that may be altered by pathophysiologic processes, such as tumor development . This property serves as the basis for the physical examination method for detecting breast cancers, or palpation. Unfortunately, palpation is a highly empirical method and is dependent on the size and location of lesions and the skill of practitioners. The inaccuracy in elasticity caused by these factors resulted in the development of more accurate elasticity measurements, which began in the 1980s .
Young’s modulus, a measure of the stiffness of an elastic material, is too difficult to be calculated in vivo. Elastography is a new technology that can be applied to ultrasound for the reconstruction of tissue elasticity . The principle of elastography is that tissue compression results in deformation within the tissue; the displacement is smaller in harder tissue than in softer tissue. Real-time ultrasound elastography (UE) allows the calculation of tissue elasticity in real time and superimposes the information in color on B-mode images, with each color representing a certain level of elasticity. Although UE has not become a routine clinical examination, it has been shown to be useful in the diagnosis of breast cancer , thyroid cancer , prostate cancer , and liver cirrhosis .
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Materials and methods
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Patients
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Methods
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Statistical Analysis
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Results
Pathologic Diagnosis
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Table 1
Histologic Diagnoses in 428 Patients with Benign or Malignant Breast Lesions
Benign Lesions ( n = 415) Malignant Lesions ( n = 144) Diagnosis_n_ Diagnosis_n_ Fibroadenoma 243 Invasive ductal carcinoma 130 Fibrocystic mastopathy 124 Papillocarcinoma 3 Papilloma 21 Invasive lobular carcinoma 3 Lipoma 7 Mucinous carcinoma 2 Chronic inflammation 5 Lymphoma 1 Hyperplasia 4 Ductal carcinoma in situ 1 Phyllodes tumor 2 Paget’s disease 2 Adenomyoepithelioma 2 Neuroendocrine carcinoma 1 Adenoleiomyoma 2 Invasive papillary carcinoma 1 Foreign body reaction 2 Tubular adenoma 1 Sclerosing adenosis 1 Hamartoma 1
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Strain Ratio of Breast Lesions
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Comparing Diagnostic Performance Between Strain Ratio Analysis and Five-point Scoring System
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Table 2
Comparison of Sensitivity, Specificity, PPV, and NPV Obtained Using Strain Ratio Measurement Method and Five-point Scoring System in the Differentiation of Benign From Malignant Breast Lesions
Lesions Method Sensitivity (%) Specificity (%) Accuracy (%) PPV (%) NPV (%) Total lesions Strain ratio 92.4 (133/144) ∗ 91.1 (378/415) 91.4 (511/559) 78.2 (133/170) 97.2 (378/389) Five-point scoring system 70.1 (101/144) 93.0 (386/415) 87.1 (487/559) 77.7 (101/130) 90.0 (386/429) Small lesions (≤10 mm) Strain ratio 95.7 (22/23) 91.6 (141/154) 92.1 (163/177) 62.9 (22/35) 99.3 (141/142) Five-point scoring system 82.6 (19/23) 92.2 (142/154) 91.0 (161/177) 61.3 (19/31) 97.3 (142/146) Median lesions (>10–20 mm) Strain ratio 88.7 (63/71) ∗ 91.0 (191/210) 90.4 (254/281) 76.8 (63/82) 96.0 (191/199) Five-point scoring system 64.8 (46/71) 93.3 (196/210) 86.1 (242/281) 76.7 (46/60) 88.7 (196/221) Large lesions (≥20 mm) Strain ratio 96 (48/50) ∗ 92.2 (47/51) 94.1 (95/101) ∗ 92.3 (48/52) 95.9 (47/49) Five-point scoring system 70 (35/50) 96.1 (49/51) 83.2 (84/101) 94.6 (35/37) 76.6 (49/64)
NPV, negative predictive value; PPV, positive predictive value.
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False-negative and False-positive Diagnoses with the Strain Ratio Assessment Method
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Table 3
Analysis of False-negative and False-positive Diagnosis by Strain Ratio Assessment Method
False-negative ( n = 11) False-positive ( n = 37) Diagnosis_n_ Diagnosis_n_ Invasive ductal carcinoma 10 Fibroadenoma 16 Paget’s disease 1 Fibrocystic mastopathy 10 Papilloma 8 Lipoma 2 Chronic inflammation 1
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Discussion
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Conclusions
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