Characterization of Solid Breast Masses Use of the Sonographic Breast Imaging Reporting and Data System Lexicon

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1 Case Series Characterization of Solid Breast Masses Use of the Sonographic Breast Imaging Reporting and Data System Lexicon Melania Costantini, MD, Paolo Belli, MD, Roberta Lombardi, MD, Gianluca Franceschini, MD, Antonino Mulè, MD, Lorenzo Bonomo, MD Objective. The purpose of this study was to determine the reliability of sonographic American College of Radiology Breast Imaging Reporting And Data System (BI-RADS) classification in differentiating benign from malignant breast masses. Methods. One hundred seventy-eight breast masses studied by sonography with a known diagnosis were reviewed. All lesions were classified according to the sonographic BI-RADS lexicon. Pathologic results were compared with sonographic features. Sensitivity, specificity, accuracy, and positive predictive value (PPV) and negative predictive value (NPV) for the sonographic BI-RADS lexicon were calculated. Results. Twenty-six cases were assigned to class 3, 73 to class 4, and 79 to class 5. Pathologic results revealed 105 malignant and 73 benign lesions. The sonographic BI-RADS lexicon showed 71.3% accuracy, 98.1% sensitivity, 32.9% specificity, 67.8% PPV, and 92.3% NPV. The NPV for class 3 was 92.3%. The PPVs for classes 4 and 5 were 46.6% and 87.3%. Typical signs of malignancy were irregular shape, antiparallel orientation, noncircumscribed margin, echogenic halo, and decreased sound transmission. Typical signs of benignity were oval shape and circumscribed margin. Conclusions. The sonographic BI-RADS lexicon is an important system for describing and classifying breast lesions. Key words: breast masses; diagnosis; sonography. Abbreviations ACR, American College of Radiology; BI-RADS, Breast Imaging Reporting and Data System; FNAC, fine-needle aspiration cytologic examination; NPV, negative predictive value; PPV, positive predictive value Received July 5, 2005, from the Departments of Bio- Imaging and Radiological Sciences (M.C., P.B., R.L., L.B.), Surgery (G.F.), and Pathology (A.M.), Catholic University, Rome, Italy. Revision requested August 9, Revised manuscript accepted for publication January 18, Address correspondence to Melania Costantini, MD, Department of Bio-Imaging and Radiological Sciences, Catholic University, Largo F. Vito 8, Rome, Italy. mcostantini@rm.unicatt.it In addition to mammography, sonography has become a standard breast-imaging procedure during the last 15 years because of rapid technological advances such as the use of all-digital high-frequency transducers of up to 13 MHz, color and power Doppler imaging, and harmonic imaging. 1 6 Although breast sonography has historically been used for differentiating fluid from solid lesions, there has been growing interest in using sonography to differentiate benign from malignant solid masses 7,8 and to avoid biopsies because of its ability to accurately identify the lesion characteristics suggestive of malignancy The sensitivity of breast sonography has been found to be superior to mammography 5,6,12 especially in premenopausal breasts, and recently, screening sonography has also been advocated for dense breasts. 13,15,16 Today, sonography plays an important role in guiding interventional procedures such as needle aspiration, core needle biopsy, and prebiopsy needle localization. 17, by the American Institute of Ultrasound in Medicine J Ultrasound Med 2006; 25: /06/$3.50

2 Characterization of Solid Breast Masses A lexicon of sonographic descriptors of breast masses with attendant assessment categories (Breast Imaging Reporting and Data System [BI-RADS]) has been developed by the American College of Radiology (ACR; Reston, VA) to enhance the clinical efficacy of breast sonography and to standardize terms for lesion characterization and reporting. The sonographic BI-RADS lexicon includes sonographic descriptors for shape, orientation, margins, lesion boundary, echo pattern, posterior acoustic features, and surrounding tissue alterations. On the basis of these descriptors, each lesion was assigned to a final assessment category. 19 The purpose of this study was to determine the reliability of the sonographic BI-RADS lexicon in differentiating benign from malignant breast masses. Cytologic or histologic results were used as the standard criterion. The objectives of our study were the following end points: (1) primary end point, diagnostic accuracy of sonographic BI-RADS classification in distinguishing benign from malignant masses; and (2) secondary end points, diagnostic sensitivity, specificity, prevalence, error ratio, positive predictive value (PPV) and negative predictive value (NPV) of sonographic BI-RADS classification. Positive and negative predictive values of each class of suggestive sonographic descriptors were also evaluated. Materials and Methods Breast masses with known diagnosis studied by sonography in our department from October 2002 to October 2004 were retrospectively reviewed. All patients who in the period of reference consecutively underwent sonographically guided fineneedle aspiration cytologic examination (FNAC) of a breast lesion entered the study. The indication for FNAC was based on a preliminary breast examination performed by us or elsewhere in accord with the attending physician. Sonography was performed with a high-resolution (10- to 13-MHz) linear array transducer and a Siemens Antares sonography unit (Siemens Medical Solutions, Sweden). The scanning protocol included both transverse and longitudinal real-time imaging. Initially all lesions underwent FNAC. The FNAC results were accepted for a definitive diagnosis only if they led to a specific benign or malignant diagnosis. The FNAC results were considered not definitive if imaging and cytologic findings were discordant, if insufficient sampling was indicated, and if the sample consisted of normal breast epithelial cells. As a specific negative result, we considered cytologic matter with no atypical characteristics and compatible with complicated cysts, fibroadenoma, galactocele, liponecrosis, inflammations such as granulomas, and fibrocystic modifications such as apocrine metaplasia. As a positive result, we considered the presence of atypical cytologic characteristics. In cases in which results of fine-needle aspiration were positive for malignancy or not definitive, surgical excision and subsequent histologic examination were performed, as in our usual protocol. In cases in which results of fine-needle aspiration were negative for malignancy, the lesion was scheduled for follow-up every 6 months. Only sonographic examinations performed in the study period by 2 radiologists experienced in breast imaging (P.B. and M.C.) were selected to prevent reading bias. The radiologists retrospectively reviewed the hard copy sonographic images of all cases without considering the clinical history or pathologic results. All lesions were classified according to the sonographic BI-RADS lexicon (Table 1), 19 and final decisions were made with consensus agreement among observers. After careful description of the lesions according to BI-RADS criteria, all lesions with the following combination of benign signs were assigned to class 3: round or oval shape, parallel orientation, Table 1. American College of Radiology BI-RADS Classification: Final Assessment Categories Assessment incomplete Category 0: need additional imaging evaluation Assessment complete (final categories) Category 1: negative Category 2: benign finding Category 3: probably benign finding; short-interval follow-up suggested Category 4: suggestive abnormality; biopsy should be considered Category 5: highly suggestive of malignancy; appropriate action should be taken Category 6: known biopsy-proved malignancy 650 J Ultrasound Med 2006; 25:

3 Costantini et al circumscribed margins, well-defined interface, enhancement or absence of posterior acoustic alterations, and absence of alterations in the adjacent tissue independent of the echoic structure. Lesions having indistinct margins or posterior acoustic shadowing as the only sign of suspicion were also placed in class 3. All lesions showing an association of at least 3 of the following signs were assigned to BI-RADS class 5: irregular shape, antiparallel orientation, noncircumscribed margins, presence of a hyperechoic halo, presence of posterior acoustic shadowing, and presence of adjacent tissue alterations independent of the echoic structure. Class 4 included all lesions that did not satisfy the criteria for benign lesions and did not have a combination of 3 signs of malignancy and therefore were indeterminate. Patient age and site and size of each lesion were also considered. Cytologic or histologic examinations were compared with sonographic features. A definitive diagnosis of atypical hyperplasia was considered malignant, whereas a definitive diagnosis of usual hyperplasia was considered benign. The diagnostic sensitivity, specificity, accuracy, prevalence, error ratio, PPV, and NPV of the sonographic BI-RADS lexicon were calculated, including class 3 in the benign group and unifying classes 4 (probably malignant) and 5 (malignant) in the malignant group. The PPV and NPV for each class and sonographic descriptor were also calculated. The PPV and NPV for each sonographic descriptor were obtained as follows: PPV for sonographic descriptor = number of cancers per sonographic feature; and NPV for sonographic descriptor = number of benign lesions per sonographic feature. Results One hundred seventy-eight breast masses in 164 female patients were included in our study. All lesions were studied with sonographically guided FNAC, and 148 of 178 underwent subsequent surgical resection. Patients in BI-RADS classes 3 and 4 (18 and 12, respectively) who had FNAC that documented only a specific benign lesion underwent sonography every 6 months (mean follow-up, 24.6 months; range, months). In particular, 24 patients reached a 2-year followup; 5 reached an 18-month follow-up; and 1 reached a 1-year follow-up. The mean age of the patients ± SD was ± years (range, years). The mean size of the lesions was ± mm (range, 4 90 mm). No prevalence of side or quadrant was observed. On the basis of sonographic BI-RADS categorization, our cases were classified as follows: 26 class 3, 73 class 4, and 79 class 5. No case was assigned to class 0, 1, 2, or 6. Cytologic and histologic results revealed 105 malignant lesions and 73 benign lesions. The total benign-malignant ratio was The NPV for class 3 was 92.3%; the PPVs for classes 4 and 5 were 46.6% and 87.3%, respectively (Table 2). Definitive diagnoses of all cases in relation to sonographic BI-RADS categorization are shown in Table 3. The prevalence of cancer in our study population was 58.98%. The sonographic BI-RADS system showed 71.3% accuracy, 98.1% sensitivity, 32.9% specificity, and a 28.6% error ratio. The PPV and NPV were 67.8% and 92.3%, respectively (Table 4). Lesions were round in 32 cases, oval in 59, and irregular in 87. Seventeen (53.1%) of 32 round lesions were benign, and 15 (46.9%) of 32 were malignant. Forty-seven (79.7%) of 47 oval lesions were benign, and 12 (20.3%) of 59 were malignant (Figures 1 and 2). There were 87 irregular, 78 malignant, and 9 benign lesions, for a PPV and NPV of 89.7% and 10.3%, respectively. No irregular lesion was placed in class 3; only 15 (20.5%) of 73 cases were placed in class 4; and 72 (91.1%) of 79 were placed in class 5 (Table 5). Margins were circumscribed in 49 cases, indistinct in 75, angular in 32, microlobulated in 6, and spiculated in 16. Only 6 (12.2%) of 49 lesions with circumscribed margins were malignant, for an NPV of 87.8%. No case with circumscribed margins was placed in class 5. Fifty (66.7%) of 75 lesions with indistinct margins were malignant, and 25 (33.3%) of 75 were benign. Angular margins were present in 32 cases, 3 benign and 29 malignant. The PPV and NPV for angular margins as a descriptor were 90.6% and 9.4%, respectively (Figures 2 and 3). Only 6 cases showed microlobulated margins, and all of them were Table 2. Distribution of Benign and Malignant Lesions for Each BI-RADS Class Lesion Type Benign, n (%) 24 (92.3) 39 (63.4) 10 (12.7) 73 Malignant, n (%) 2 (7.7) 34 (46.6) 69 (87.3) 105 Total J Ultrasound Med 2006; 25:

4 Characterization of Solid Breast Masses Table 3. Definitive Diagnosis in Relation to Sonographic BI-RADS Categorization Definitive Diagnosis Complicated cyst (5) 3 (2) 0 8 Fibroadenoma 11 (9) 12 (7) 0 23 Complex fibroadenoma Galactocele (1) Fat necrosis (2) Sclerotic lesion Inflammatory changes 0 9 (2) 3 12 Fibrocystic changes 2 (1) 5 (1) 3 10 Papilloma Tubular adenoma Usual hyperplasia Atypical hyperplasia Ductal carcinoma in situ Cancer in fibroadenoma Phyllodes tumor Mucinous carcinoma Ductal carcinoma Lobular carcinoma Tubular carcinoma Lobular/tubular carcinoma Papillary carcinoma Intracystic carcinoma Metastasis Total The diagnosis of cases in parentheses was exclusively cytologic, whereas for all other cases, the diagnosis was histologic. malignant, for a PPV of 100% (Figure 4). Lesions with angular and microlobulated margins were placed in classes 4 and 5 only. Two of 16 lesions with spiculated margins were benign, and 14 of 16 were malignant, for a PPV and NPV of 87.5% and 12.5%. Lesions with spiculated margins were placed in class 5 only (Table 6). The echo pattern was hypoechoic in 151 cases, isoechoic in 2, hyperechoic in 3, and complex in 22. One hundred fifty-one (84.8%) of 178 lesions appeared hypoechoic on sonography; in particular, the hypoechoic pattern represented 97.5% (77/79 cases) of echo patterns in class 5 and 76.7% (56/73) and 69.2% (18/26) in classes 4 and 3, respectively. The PPV for the hypoechoic pattern was 64.2% (97/151). All hyperechoic lesions were benign; 50% of isoechoic and 68.8% of complex lesions were benign (Table 7). A parallel orientation was present in 84 cases (38 malignant and 46 benign lesions), for a PPV and NPV of 45.2% and 54.8%, respectively. An antiparallel orientation was present in 94 cases (67 malignant and 27 benign lesions), for a PPV and NPV of 71.3% and 28.7% (Figure 5). The horizontal-vertical diameter ratios of different BI-RADS classes are reported in Table 8. The horizontal-vertical diameter ratio decreased proportionally to the BI-RADS class (from 1.81 to 1.15). Table 4. Distribution of False- and True-Positive and -Negative Results Based on Pathologic Diagnosis and Diagnostic Discrimination Indicators Test Result D+ D Total T+ 103 (TP) 49 (FP) 152 T 2 (FN) 24 (TN) 26 Total Figure 1. Oval hypoechoic mass with circumscribed margins (BI-RADS class 3). Malignancy is highly unlikely. Histologic examination confirmed a benign lesion (fibroadenoma). Parameter Formula n Value Sensitivity TP/(TP + FN) 103/( ) 0.98 Specificity TN/(TN + FP) 24/( ) 0.32 PPV TP/(TP + FP) 103/( ) 0.67 NPV TN/(TN + FN) 24/(24 + 2) 0.92 Accuracy (TP + TN)/total ( )/ Prevalence (TP + FN)/total ( )/ Error ratio (FP + FN)/total (49 + 2)/ D+ indicates disease-positive; D, disease-negative; FN, falsenegative; FP, false-positive; T+, test-positive (lesions assigned to classes 4 and 5); T test-negative (lesions assigned to class 3); TN, true-negative; and TP, true-positive. 652 J Ultrasound Med 2006; 25:

5 Costantini et al One hundred nineteen (66.9%) of 178 cases showed an abrupt interface, and 59 (33.1%) of 178 showed an echogenic halo. The PPVs for these 2 lesion boundary descriptors were 45.4% and 86.4%, respectively. The echogenic halo was a rare finding in class 4 (only 9.6% of cases placed in class 4) because it is often associated with other suggestive signs that affect the judgment of malignancy. Its presence showed a very high predictive value for malignancy (Table 9 and Figure 5). The description of posterior acoustic features is reported in Table 10. Eighty-five (47.8%) of 178 cases showed no posterior acoustic features, and most of these lesions were placed in class 4. The absence of posterior acoustic features was a nonspecific sign (NPV, 52.9%). Twelve of 17 lesions with posterior enhancement were benign, for an NPV of 7.06%, and 5 of 17 were malignant (3 class 4, 1 class 3, and 1 class 5). Seventy-six lesions revealed posterior acoustic shadowing (59 class 5, 16 class 4, and 1 class 3). The PPV for this sign was 78.9% (89.8% for class 5 and 43.8% for class 4) (Figure 5). The only lesion placed in class 3 with acoustic shadowing was benign. Most of our cases did not show surrounding tissue alterations. Only 12 malignant lesions showed architectural alterations or skin thickening (Table 11 and Figure 6). In class 4, a high number of malignant cases were associated with a hypoechoic echo pattern (85.3% versus 69.2% of benign lesions), indistinct Table 5. Shape in Relation to Sonographic BI-RADS Classification Shape B M B M B M B M Total Round Oval Irregular margins (70.6% versus 48.7%), and an antiparallel orientation (73.5% versus 35.9%), as well as a round or irregular shape. Many cases of benign lesions were hypoechoic with indistinct margins but were often associated with an oval shape (74.4%). Only a few cases showed an echogenic halo or posterior acoustic features, and no case showed surrounding tissue alterations (Figure 7). Discussion Because of the frequent overlap of radiologic signs, breast lesions indicative of malignancy detected on sonography have to be examined with biopsy to prove their malignancy or benignity The large number of biopsies performed for benign abnormalities because of patient fear, physician uncertainty, or standard protocols has long been recognized as an additional problem. 20 Excessive biopsies have adverse effects on society, increasing the costs of screening projects and health care. 10,20,21 Figure 2. Oval hypoechoic mass with angular margins, an abrupt interface, and no posterior acoustic features (BI-RADS class 4). Angular margins are suggestive of malignancy, and biopsy should be considered. The definitive diagnosis was medullary carcinoma. Figure 3. Irregular antiparallel hypoechoic mass with angular margins, an abrupt interface, and no posterior acoustic features. This lesion appears highly suggestive of malignancy (BI-RADS class 5). Invasive ductal carcinoma was diagnosed. J Ultrasound Med 2006; 25:

6 Characterization of Solid Breast Masses Figure 4. Oval hypoechoic mass with microlobulated margins, an abrupt interface, and no posterior acoustic features (BI-RADS class 5). Microlobulated margins may be a suggestive sign of malignancy, and in their presence, biopsy should be considered. In this case, invasive tubular carcinoma was diagnosed. Breast sonography is not used to its full capacity if it is restricted to the differentiation between cystic and solid lesions and evaluation of dense breasts. To decrease the number of biopsies for benign lesions, sonography should be exploited for accurate interpretation of a lesion s characteristics of suspicion. 6,7,12 Improvements have been achieved in sonographic diagnosis by the ACR with the introduction of the BI-RADS classification, which helps the radiologist in describing sonographic features and defining the final assessment category that is associated with the most appropriate clinical management of the case. 19 If these reliable Table 6. Margin Distribution in Relation to Sonographic BI-RADS Classification Class Distribution B M B M B M B M Total Circumscribed Indistinct Angular Microlobulated Spiculated criteria were strictly applied starting from the initial radiologic report, the number of biopsies for benign lesions could be decreased. Our study confirms the high sensitivity (identification of malignant lesions in patients with breast cancer; 98.1%) and the high NPV (identification of true negative findings in disease-free patients; 92.3%) of the sonographic BI-RADS classification. However, the BI-RADS had low specificity (32.9%) because of the high number of false-positive findings (49 cases). Thirty-nine of 49 cases with false-positive findings were assigned to class 4, and 10 of 49 were assigned to class 5. Clearly, the major problem in differentiating benign from malignant lesions is related to the overlap of lesions placed in class 4 (benignmalignant ratio, 1.14). In a large series of patients, Stavros et al 7 reported 98.4% sensitivity, 67.8% specificity, 38% PPV, 99.5% NPV, and 72.9% accuracy. In their study, the PPV was considerably lower than ours (38% versus 67.76%) probably in relation to the different prevalence of breast cancer (17% versus 58.98%) and to the different patient selection criteria. Predictive values were highly influenced by the sensitivity, specificity, and prevalence; particularly, the prevalence increase led to a PPV increase. In our study, the sonographic accuracy (71.3.%) in differentiating benign from malignant lesions with the use of ACR BI-RADS sonographic categorization was similar to the results of Stavros et al. 7 In our study, the NPV for class 3 was 92.3%. In class 3, 2 of 26 cases were malignant, for a PPV of 7.7%. However, our results were hindered by the low number of lesions assigned to this class. Only lesions that underwent cytologic or histologic examination were enrolled in our study, and only a small number of women with probably benign lesions and proved diagnoses were included. In these cases, cytologic examination was performed because of the patient s or physician s choice. The risk of malignancy for lesions designated BI-RADS category 3 should be less than 2%. The benign nature of such lesions can be presumed by showing stability on surveillance over an interval of 2 to 3 years. The characterization of these probably benign lesions is an important and frequently used tool for breast radiologists to avoid biopsies. Most lesions placed in class 3 proved to be fibroadenomas, and temporal stability at follow-up corroborated our diagnosis of 654 J Ultrasound Med 2006; 25:

7 Costantini et al a probably benign lesion. If the benign-appearing mass enlarges at follow-up, we tentatively suggest that the mass has converted to a BI- RADS category 4 lesion, for which biopsy would be appropriate In our study, other than in patients with complicated cysts that decreased in size during FNAC, none of the lesions placed in class 3 showed morphologic or dimensional changes during follow-up. In our study, the PPVs for classes 4 and 5 were 46.6% and 87.3%, respectively. The assignment of a breast mass to category 4 has a clinical impact similar to that of the malignant classification (class 5) because both require biopsy. The lesions assigned to class 4 had 1 or 2 suggestive criteria. In class 4, 34 cases were malignant, and 39 were benign. In this class, we observed a large variety of shapes, margins, and echo patterns. A careful study of the sonographic descriptors associated with class 4 showed that the lesions that proved to be malignant were frequently associated with a hypoechoic echo pattern, indistinct margins, and antiparallel orientation. Although many benign lesions placed in class 4 were hypoechoic with indistinct margins, they were associated with an oval shape and a parallel orientation. In this category, the orientation and shape parameters offer the most reliable criteria in differentiating benign from malignant lesions. We noted that only a few cases placed in class 4 showed an echogenic halo and posterior acoustic features and that no case showed surrounding tissue alterations. In presence of these 3 sonographic characteristics, the lesion was usually placed in class 5. However, these criteria were not sufficient to discriminate benign from malignant masses, and biopsy always had to be performed. Of the lesions assigned to class 5, 69 were malignant, and 10 were benign. These lesions generally showed more than 3 suggestive characteristics of malignancy: irregular shape, indistinct or angular margins, hypoechoic echo pattern, antiparallel orientation, echogenic halo, and posterior acoustic shadowing. We noted that false-positive results in classes 4 and 5 were due to fibroadenomatous and fibrocystic changes. Shape is one of the most reliable criteria for differentiating benign from malignant breast masses. Hong et al 22 reported a 62% PPV for an irregular shape and an 84% NPV for an oval shape. In our study, an irregular shape was associated with the highest PPV (89.7%), whereas an oval shape was associated with the highest NPV Table 7. Echo Pattern Descriptor Related to Sonographic BI-RADS Classification Class Pattern B M B M B M B M Total Hypoechoic Isoechoic Hyperechoic Complex (80.3%). A round shape was a nonspecific finding. In evaluating the sonographic margins descriptor, we found that only 16 lesions showed spiculated margins, and all of them were assigned to class 5. The relatively low number of spiculated masses was probably attributable to the small size of the lesions studied (the mean diameter of lesions placed in class 5 was <13 mm) and to the use of a new margin descriptor. Part of the reason Figure 5. Irregular antiparallel hypoechoic mass with spiculated margins, an echogenic halo, and posterior acoustic shadowing (BI-RADS class 5). This lesion appears highly suggestive of malignancy, but histologic examination revealed a benign nature (sclerotic lesion). It was false-positive sonographic finding. J Ultrasound Med 2006; 25:

8 Characterization of Solid Breast Masses is that the thick halo in most cases represents spiculations too small to be resolved sonographically. With the sonographic classification, the introduction of the addition of further margin descriptors led to subclassification of noncircumscribed lesions to different categories. The PPV of angular and microlobulated margins was higher than that of spiculated margins. Indistinct Table 8. Horizontal and Vertical Diameters Compared With Sonographic BI-RADS Classification Diameter (mean) Class 3 Class 4 Class 5 Horizontal, mm Vertical, mm Horizontal-vertical ratio Table 9. Lesion Boundary Descriptor in Relation to Sonographic BI-RADS Classification Descriptor B M B M B M B M Total Abrupt interface Echogenic halo margins are nonspecific signs. The NPV for a circumscribed margin was very high. In the study by Hong et al, 22 spiculated and circumscribed margins showed an 86% PPV and a 90% NPV. In our study, 84.3% of lesions appeared hypoechoic on sonography. The hypoechoic echo pattern has a lower PPV than irregular shape and noncircumscribed margins, but the reliability of this feature increases if it is associated with the other suggestive findings (PPV was 87.0 in class 5 versus 51.8 in class 4). According to other authors, 5,23 26 shape, margins, and echo pattern were the significant factors for differential diagnosis on sonography. An antiparallel orientation was an important predictive malignant sign if associated with other predictive malignant descriptors. The PPVs of antiparallel findings were 86.0% for lesions placed in class 5 and 56.2% for those placed in class 4. The orientation parameter was strictly associated with the lesion shape. However, all oval lesions were parallel, whereas round masses had an antiparallel orientation. Irregularly shaped lesions were often associated with an antiparallel orientation. The horizontal-vertical ratio proportionally decreased with the BI-RADS class. Similar to the shape, the antiparallel orientation was a useful criterion for differentiating benign from malignant. 23,24 In an evaluation of characteristic Table 10. Posterior Acoustic Features and Sonographic BI-RADS Classification Feature B M B M B M B M Total Enhancement No posterior alteration Shadowing Figure 6. Irregular hypoechoic spiculated mass with surrounding tissue alteration. The lesion altered the normal tissue planes (the glandular-fat line is stopped by the lesion). The malignant process extend to the skin, with straightening and thickening of the Cooper ligaments (BI-RADS class 5). Invasive ductal carcinoma was diagnosed. Table 11. Surrounding Tissue Appearance and Sonographic BI-RADS Classification Appearance B M B M B M B M Total Enhancement No alterations Architectural distortion Skin thickening J Ultrasound Med 2006; 25:

9 Costantini et al malignant mass features, Murad and Bari 24 included width to an anteroposterior dimension ratio of 1.4 or less. Our results confirm this value as a correct threshold for assigning a lesion to class 3 (1.81) or 4 and 5 (1.38 and 1.15). Hong et al 22 reported a 78% NPV for a parallel orientation and 69% PPV for an antiparallel orientation. Our study showed a similar PPV (71.3%) for the antiparallel orientation. However, the parallel orientation showed a lower NPV (54.8%) than that reported by Hong et al. 22 This difference probably is attributable to the presence of 38 malignant masses with a parallel orientation and a round or irregular shape. The echogenic halo was a rare finding in class 4 and a typical finding of lesions placed in class 5. Its presence showed a very high predictive malignant value (86.4%). An abrupt interface showed a 54.6% NPV; this descriptor was nonspecific. Shadowing of acoustic transmission is the result of attenuation of the sound beam by the desmoplastic reaction to breast cancer rather than being caused by the tumor itself. 6 Seventysix lesions revealed posterior acoustic shadowing; the PPV for this sign was 78.94% (89.83% for class 5 and 43.75% for class 4). The only lesion placed in class 3 with acoustic shadowing was benign. Although posterior acoustic shadowing is a sonographic feature that is more commonly associated with breast malignancies, this sonographic finding may also be seen in benign breast lesions. 6,27 In our series, 16 of 76 lesions with shadowing were benign (more frequently, a sclerotic tissue lesion was found). Figure 7. Round hypoechoic mass with indistinct margins and enhancement (BI-RADS class 3). A complicated cyst was diagnosed. Thin bilateral edge shadows are regarded as criteria of benign lesions. 23 Although the presence of shadowing is worrisome for malignancy, we think that neither normal sound transmission nor increased through-transmission is necessarily reassuring. In our study, 5 lesions with enhancement and 40 with no posterior acoustic features were malignant. According to other authors, 7,23 both normal and enhanced throughtransmission should be considered indeterminate findings. Most of our cases did not show surrounding tissue alterations, probably because of the small sizes of the lesions. Only 12 tumors showed architectural alterations or skin thickening, showing that the presence of these features were highly specific for malignancy and suggestive of advanced disease. We recognize some limitations in our study. Data of lesions attributed to classes 1 and 2 and those included in class 3 with no cytologic or histologic examinations were not collected. We have evaluated the contribution of sonography in a nonrandomized female population. The women who underwent sonography in the breast unit of our department were advised by our physicians or came to the breast unit voluntarily for annual breast examination. Sonographic examinations were performed by dedicated radiologists whose work might have been more accurate than that performed in general radiology practice. Fineneedle aspiration cytologic examination is not a good reference standard in the absence of at least a 2-year follow-up. Finally, case evaluation was retrospective, and the sample size was relatively small. Our study confirms that the ACR BI-RADS sonographic lexicon is an accurate system for describing breast lesions. In the revision of our study, we noted that echographic signs such as hypoechogenicity and indistinct margins are often less predictive of malignancy compared with an irregular shape, spiculated, angular or microlobulated margins, a hyperechoic halo, and posterior acoustic shadowing. Some echographic signs associated with benign lesions were often shown to be associated with malignant lesions, such as a well-defined interface, a parallel orientation, and absence of posterior acoustic signs. Oval shape, parallel orientation, circumscribed margins, and a hyperechoic echo pattern better characterize benign lesions. J Ultrasound Med 2006; 25:

10 Characterization of Solid Breast Masses As for indistinct margins as an echographic descriptor, its PPV, as we expected, was lower than others (66.7%) because we included class 3 lesions, which have indistinct margins as a single suggestive sign. The echographic descriptors of the 2 class 3 lesions found to be 2 small ductal carcinomas were as follows: (1) oval shape, hypoechoic structure, indistinct margins, welldefined interface, enhancement, and absence of adjacent tissue alterations; and (2) oval shape, isoechoic echo pattern, circumscribed margins, well-defined interface, and absence of acoustic posterior alterations and adjacent tissue alterations. One of the 2 lesions had indistinct margins. Had we not placed in class 3 2 lesions with the only indistinct margins as the only suggestive sign (1 shown to be malignant and the other benign), the NPV of class 3 would have increased, reaching 96%. As for the only lesion with posterior acoustic shadowing present in class 3, it was shown to be benign. However, because posterior acoustic shadowing is a sign highly predictive of malignancy, lesions with this echographic descriptor should not be placed in class 3, even though it is the only suggestive sign. Our findings indicate that only lesions associated with all predictive benign signs should be placed in class 3 (patients to be followed-up only and for whom biopsy is not required). Apart from the PPV or NPV of each sign, for tumor heterogeneity, an overall evaluation of the lesion based on the association of the different signs is necessary. This is the only way to distinguish really benign lesions and those with a very low probability of malignancy (in which there is an association of benign predictive signs) from malignant ones and those with a high probability of malignancy (in which multiple signs predictive of malignancy are associated), from indeterminate ones. The latter should be studied (with cytologic or histologic examination) despite undercategorization attempted to avoid biopsy for a high number of benign lesions. On the basis of a careful description of the lesion and correct association of the different signs, those lesions that are minimally or highly suggestive and require biopsy could be distinguished from probably benign lesions, which can undergo strict follow-up. There were hardly any benign-looking lesions that proved to be malignant because of the very high NPV of sonography. However, their discriminating power was not absolute. We think that practice and periodic review of cases should be performed for accurate detection and interpretation of sonographic descriptors. However, further prospective randomized trials are needed to confirm our findings. References 1. American College of Radiology. ACR Standards Reston, VA: American College of Radiology; Baker JA, Soo MS. Breast US: assessment of technical quality and image interpretation. Radiology 2002; 223: Jackson V, Reynolds H, Hawes D. Sonography of the breast. Semin Ultrasound CT MR 1996; 17: Baker JA, Soo MS, Rosen EL. Artifacts and pitfalls in sonographic imaging of the breast. AJR Am J Roentgenol 2001; 176: Rizzatto GJ. Towards a more sophisticated use of breast ultrasound. Eur Radiol 2001; 11: Schroeder RJ, Bostanjoglo M, Rademaker J, Maeurer J, Felix R. Role of power Doppler techniques and ultrasound contrast enhancement in the differential diagnosis of focal breast lesions. Eur Radiol 2003; 13: Stavros AT, Thickman D, Rapp CL, Dennis MA, Parker SH, Sisney GA. Solid breast nodules: use of sonography to distinguish between benign and malignant lesions. Radiology 1995; 196: Skaane P, Engedal K. Analysis of sonographic features in the differentiation of fibroadenoma and invasive ductal carcinoma. AJR Am J Roentgenol 1998; 170: Liberman L. Clinical management issues in percutaneous core breast biopsy. Radiol Clin North Am 2000; 38: Parker S, Stavros A, Dennis M. Needle biopsy techniques. Radiol Clin North Am 1995; 33: Flobbe K, Bosch AM, Kessels AG, et al. The additional diagnostic value of ultrasonography in the diagnosis of breast cancer. Arch Intern Med 2003; 63: Leconte I, Feger C, Galant C, et al. Mammography and subsequent whole-breast sonography of nonpalpable breast cancers: the importance of radiologic breast density. AJR Am J Roentgenol 2003; 180: Kolb T, Lichy J, Newhouse J. Occult cancer in women with dense breasts: detection with screening US diagnostic yield and tumor characteristics. Radiology 1998; 207: Benson SR, Blue J, Judd K, Harman JE. Ultrasound is now better than mammography for the detection of invasive breast cancer. Am J Surg 2004; 188: Rahbar G, Sie AC, Hansen GC, et al. Benign versus malignant solid breast masses: US differentiation. Radiology 1999; 213: J Ultrasound Med 2006; 25:

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