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Sonographic Features of Benign Breast Masses: A Case Review
Cathie Scholl, BS, RDMS, RVT
*Assistant Professor, Program Director, Diagnostic Medical Sonography, Central Ohio Technical College, Newark, Ohio.
Address correspondence to: Cathie Scholl, BS, RDMS, RVT, Assistant Professor, Program Director, Diagnostic Medical Sonography, Central Ohio Technical College, 1179 University Drive, Newark, OH 43055. E-mail: firstname.lastname@example.org.
Although breast imaging is most routinely thought of as a screening and diagnostic tool to detect and manage breast cancer, benign breast lesions are vastly more common than malignant lesions and often require accurate diagnosis to rule out cancer and determine the best treatment course. Breast ultrasound, in particular, is routinely performed to distinguish between fluid-filled breast cysts that usually require no further treatment, and solid masses that require biopsy and follow-up care. Through a series of case studies, this article will provide an overview of common presentations of benign breast lesions and their appearance on ultrasound.
Breast imaging is most often thought of as a screening procedure to rule out malignancy. However, benign lesions are found more often than malignant lesions and often require diagnostic imaging and follow-up care. When assessing a breast mass, ultrasound is often necessary to distinguish between fluid-filled cysts and solid masses. This distinction is important for the purposes of patient treatment and management. Masses that meet simple cystic criteria are essentially always benign and usually require no follow-up treatment. The same is not true for smooth, round, or oval solid masses. These lesions may require short-term interval follow-up examinations or biopsy. Although the vast majority of these solid masses are benign (96%-98%), 2% to 4% will prove to be malignant.1 Sonography has the potential to prevent unnecessary biopsies and reduce the number of short-term follow-up examinations by determining the tissue characteristics of nonpalpable mammographic abnormalities and palpable lumps,2 and all radiology professionals, including radiologic technologists, should be familiar with common ultrasound findings with benign breast lesions. It is for this reason that this article will provide an overview of the sonographic appearance of benign lesions and case studies that present common benign breast pathologies.
The Utility of Ultrasound in Benign Breast Disease
Although mammography is the established gold standard for breast cancer screening and diagnosis, ultrasound offers a diagnostic advantage to mammography or clinical examination in many presentations of benign breast disease. An early study of 2500 women found that ultrasound was particularly useful in differentiating between cysts and solid masses in palpable breast masses; differentiating between cysts and solid masses in nonpalpable masses identified through screening mammogram; and diagnosing symptomatic areas that are imaged as uniformly dense fibroglandular tissue on mammogram.3
Computer-aided diagnosis (CADx) may be used to help radiologists distinguish between benign and malignant breast lesions imaged on ultrasound. One study found that CADx improved the ability to detect and characterize malignant lesions imaged on ultrasound among nonradiologists, but was only marginally helpful in improving these capabilities among experienced radiologists.4
Methods to improve the ability of CADx to confirm or rule out breast cancer have been investigated to improve the diagnostic strength of breast ultrasound. One study reported the successful use of a database of sonographic images, with a 19% prevalence of malignant lesions, to improve automated confidence levels provided through CADx.5 Another innovative algorithm achieved automated region of interest (ROI) labeling in CADx, which resulted in similar correlation with ROI identified by expert radiologists.6
Automated support to CADx represents only one of the innovative processes that have been investigated to improve the diagnostic strength of ultrasound to distinguish between benign and malignant breast disease. Although new techniques may reduce the need for biopsy, some presentations of breast masses are difficult to distinguish between malignant and benign, and therefore will continue to require biopsy.
Benign breast disease encompasses a wide range of disorders, some of which may be associated with an increased risk of the subsequent development of breast cancer. However, many presentations of benign breast disease are not associated with an increased risk of breast cancer. In general, the incidence of benign breast disease is most common in women between the ages of 20 and 50, whereas the incidence of breast cancer increases after menopause. Although clinical examination findings and patient self-assessment of palpable masses are important, clinicians rely on appropriate imaging studies to arrive at an accurate diagnosis and guide therapy. The accurate diagnosis of benign disease, often with the use of ultrasound, can rule out malignancy and sometimes avoid the need for unnecessary surgical procedures, especially in younger women who are more likely to present with benign breast disease.7
Common Sonographic Presentations in Benign and Malignant Breast Disease
Both mammography and sonography rely on several characteristics to determine whether the mass is suggestive of benign or malignant disease. When attempting to characterize a mass sonographically, several features must be scrutinized. These include clarity and contour of margins, shape and orientation, echogenicity and echo texture, effects on distal echoes, vascularity, and compressibility.
Typical Malignant Presentations
The typical sonographic presentation of a malignancy is an irregular, heterogeneous, hypoechoic mass with angular margins and spiculations. These masses tend to have a "taller-than-wide" orientation and demonstrate acoustic shadowing. Only after determining the absence of any suspicious findings can a nodule be evaluated as probably benign or American College of Radiology Breast Imaging Reporting and Data System (BIRADS) category 3, which means that the lesion is probably benign but short-interval follow-up of the lesion is suggested.
Benign nodules are typically well defined with smooth margins or macrolobulated with no more than 3 to 4 mild lobulations. These nodules are usually round or ovoid in shape with a "wider-than-tall" appearance indicating an orientation that is parallel to the chest wall. Echo texture is often homogeneous with an isoechoic, hyperechoic to mildly hypoechoic echogenicity. Several benign masses will exhibit mild acoustic enhancement and be slightly compressible. The presence of vascularity is variable and dependent on the histology of the nodule.
Although mammographers, sonographers, and other radiology professionals have these general characteristics to guide them in their differentiation of breast lesions, it is important to discuss common nonmalignant lesions in the context of daily practice. The following clinical cases and supporting images provide a pictorial overview of benign breast lesions encountered in clinical practice.
Case #1: Simple Breast Cyst
A 47-year-old female who had undergone previous breast augmentation was referred for diagnostic imaging by her obstetrician/gynecologist with a palpable lump within the right breast. The patient had a benign screening mammogram 4 months prior to discovering the palpable lump (Figure 1). Breast ultrasound demonstrated an anechoic structure with acoustic enhancement and well-defined borders, suggesting a simple cyst (Figure 2). The implant was also noted and appeared to be intact.
Simple Breast Cysts in Clinical Practice
Simple cysts are localized areas of duct dilatation that occur at the terminal portion of the lobular ducts. Cysts may result from an overproduction of fluid or an obstructed duct that disrupts the normal flow and reabsorption of fluid. These secretions accumulate, forming a cyst. Simple cysts are very common masses that occur most often in women aged 35 to 50 years.8 In fact, simple cysts are so commonly encountered that they are often considered a variation of normal anatomy.2 Simple cysts are commonly the cause of a palpable lump, second only to a fibroglandular ridge of normal breast parenchyma.
In mammography studies, cysts present as circular or oval low-density masses with smooth margins. To be classified as a simple cyst, the lesion must demonstrate specific sonographic characteristics. Upon sonography, a simple cyst will appear as a well-defined, round or oval-shaped lesion with smooth thin margins, distal acoustic enhancement, and the absence of internal echoes. Cysts are usually compressible with minimal pressure from the transducer and elicit no Doppler signal. Sonography has been reported to have 98% accuracy detecting cysts.8
Simple cysts generally do not require any treatment and often resolve spontaneously. Cyst aspiration could be considered if the cyst is large and causes the patient discomfort. Routine yearly mammography was recommended for this patient. If the cyst is present on the next mammogram, but appears to be stable, sonography will not be necessary. If any changes are suspected, sonography is warranted to evaluate potential changes in the characteristics of the cyst.
A complex cyst is any cyst that does not meet the strict criteria for a simple cyst.2 The absence of any of the criteria excludes a cyst from being characterized as simple and requires the characterization of complex or complicated.2 Complex cysts are quite common in patients with fibrocystic breast disease. These cysts may contain internal echoes, as a result of hemorrhage or infection, and may demonstrate wall thickness.8 Ultrasound images of complex cysts are presented in Figures 3 and 4.
Cyst aspiration with cytology/histology evaluation or short-term interval follow-up can be considered for patients who present with these lesions. In a patient with a history of fibrocystic condition, a short-term follow-up of 6 weeks, 4 months, or 6 months may be recommended. Complex cysts that contain thick septations, mural nodules, and a fibrovascular stalk or have a microcystic microlobulated appearance are suspicious for neoplasm. Aspiration of these complex cysts with cytology evaluation, biopsy with histology evaluation of the mural nodule, or excision is warranted.
Figure 3 demonstrates a complex cyst with a debris level. Changing the patient position during examination can further distinguish debris levels from intracystic mural nodules. Mural nodules will not move with changes in patient position because they are adherent to the wall of the cyst, whereas debris will change position to the dependent portion of the cyst. A short-term interval follow-up of 6 months was suggested for this patient.
Figure 4 represents an indeterminate complex nodule. An aspiration was suggested for this patient due to a recent diagnosis of invasive ductal carcinoma of the contralateral breast 6 months prior to this examination. This nodule proved to be ductal carcinoma in situ thus suggesting that personal history is sometimes more crucial than imaging appearance alone.
Figures 5 and 6 demonstrate complex cystic areas with an internal soft tissue component. Biopsy was performed on both of these lesions, confirming the diagnosis of benign intracystic papilloma. These lesions occur from a growth within a duct that eventually results in ductal obstruction and cyst formation. Both patients presented with bloody nipple discharge, the classic clinical symptom of papillomas.
Intracystic lesions that result from fibrocystic condition are more common than intracystic papillomas or carcinomas. Therefore, it is helpful to try to characterize these lesions sonographically. The primary difference between the lesions associated with fibrocystic condition and true intracystic lesions is in the formation of the cyst versus the mural nodule. In cases of true intracystic papillomas, the nodule grows into the duct, causing the cyst to form. With fibrocystic condition, the cyst forms first, then the lesion develops within the existing cyst. The growth of true intracystic papillomas and carcinomas into surrounding ducts results in 2 distinct sonographic findings. These include: (1) the wall to which the mural nodule attaches may be angular or irregular and may not have an echogenic capsule (as demonstrated with both patients above); or (2) the papillomas and carcinomas that extend into the draining ducts beyond the cyst may grossly distend the duct, changing the normal spherical or oval cyst to a keyhole shape.2
Case #2: Sebaceous Cyst
A 67-year-old female presented with a superficial palpable mass within the left breast. Baseline mammography demonstrated breast tissue that was slightly denser in the periareolar region of the left breast, and a superficial nodule corresponding to the palpable area (Figure 7). A left breast ultrasound demonstrated a cutaneous lesion at the 2 o'clock axis (Figure 8), most likely representing a sebaceous cyst.
Identifying Sebaceous Cysts in Breast Studies
Sebaceous cysts are formed as a result of obstructed sebaceous glands or hair follicles. These cysts contain an oily substance, and are therefore often characterized by internal echoes that may be seen on ultrasound. They are typically located at the inferior and medial breast margins, or near the axilla. In mammographic studies, sebaceous cysts present as cyst-like masses under the skin. In general, 3 sonographic findings are used to confirm the origin of the cyst is in the skin. Findings consistent with a sebaceous cyst include a lesion that lies entirely within the skin (as demonstrated in Figure 8); a lesion with a vast majority lying within the subcutaneous tissues, with a "claw sign" of hyperechoic skin around the edge of the lesion; or a lesion that lies entirely within the subcutaneous fat, but the gland neck or hair follicle within which the lesion arose can be shown coursing through the skin.
Another consideration is that sebaceous cysts may also become inflamed. If inflammation is present, hyperemia may be demonstrated with color Doppler. Sebaceous cysts that are not inflamed do not demonstrate flow on Doppler imaging. Due to the superficial location of sebaceous cysts, a standoff pad may be required to accurately image the cyst. Standoff pads create depth allowing the lesion to be viewed slightly deeper within the near field of the image where resolution is improved. In the absence of a standoff pad, acoustic gel can be used. The technologist should apply enough gel so that there is a small pile over the lesion. The transducer should then be placed on the gel, using very little pressure so that the gel is not compressed. This will add depth to the image as well. Echogenic artifact anterior to the lesion may be noted on the image as a result from the bubbles within the gel. Treatment for sebaceous cysts may include antibiotic therapy, compression with heat to promote resolution or referral to a dermatologist for removal.
Case #3: Fibroadenoma
A 36-year-old female presented for screening baseline mammogram. A prominent nodular density was noted in the retroareolar region of the right breast (Figure 9). Ultrasound demonstrated a macrolobulated, well circumscribed, hypoechoic, solid nodule (Figure 10), suggesting a diagnosis of fibroadenoma.
Fibroadenomas arise from the terminal ductolobular unit and contain variable amounts of both stromal and epithelial elements.2 Fibroadenomas develop under the influence of estrogen, and are therefore more common in women who are 15 to 35 years of age. These masses are also more common in women of African American descent. These masses can grow quickly, but typically do not become larger than 3 cm. Fibroadenomas also tend to grow rapidly during the first trimester of pregnancy, when estrogen levels are high.2
Fibroadenomas are visualized on mammography as well circumscribed, round, ovoid, or gently lobulated in shape and isodense.2 Older, degenerating fibroadenomas often develop internal calcifications that resemble popcorn on a mammogram.8 The classic presentation of a fibroadenoma on sonography is an elliptical or gently lobulated mass with a "wider-than-tall" orientation, isoechoic or mildly hypoechoic properties, completely covered by a thin echogenic capsule, and normal to increased distal acoustic enhancement. Upon palpation, the nodule is mobile, not fixed. It may also be slightly compressible with mild transducer pressure. Color Doppler may also demonstrate minimal vascularity within or around the periphery of these masses.
Treatment can be conservative with short-term interval follow-up for probable fibroadenomas. Documented stability over 2 years in successive 6-month intervals ensures a benign lesion. After this time frame, no further treatment is necessary. If any significant growth or change is noted within the 2 years, biopsy is warranted. Biopsy can also be performed for immediate confirmation of a fibroadenoma, if the patient prefers this treatment course. After 1 year, this patient's mass was noted to have grown just over 1 cm from its original size. Biopsy was suggested and surgical excision was performed. The pathology report still indicated a benign fibroadenoma.
Case #4: Giant Fibroadenoma
A 28-year-old female presented with a palpable mass in the right breast. The patient stated that the mass had been there for years, but recently started to enlarge. Sonography demonstrated a lobulated, primarily solid, hypoechoic mass with vascularity noted (Figure 11). A biopsy confirmed the diagnosis of a fibroadenoma with fibrocystic changes. The patient elected to have the mass surgically removed.
Giant fibroadenomas and juvenile fibroadenomas can grow rapidly, often becoming as large as 6 to 10 cm. These fibroadenomas are variants of the adult type with the stroma being more cellular than the adult version. Color Doppler is often used with the assumption that benign masses demonstrate little to no flow whereas malignancies demonstrate high vascularity. In actuality, fibroadenomas with cellular stroma and some complex fibroadenomas often have more internal flow than the average low- or intermediate-grade carcinomas.2 Some low-grade, less cellular malignancies may produce very little detectable flow. Therefore, clinicians cannot assume that the presence of flow suggests malignancy, or that the lack of flow suggests a benign lesion.
Although Doppler flow cannot be used to confirm or rule out the presence of a malignancy, spectral analysis can be helpful in better evaluating the resistance of flow in a lesion, and can help differentiate between benign and malignant masses. Calculating a resistive index from 2 locations (preferably one internal and one peripheral) from a mass can further help to differentiate the potential of a benign versus malignant mass. Malignant lesions typically demonstrate high resistive patterns within the lesion and slightly less resistance within the peripheral vessels. Benign lesions demonstrate less resistance in both the internal and peripheral vessels (Figure 12).
Case #5: Lipoma
A 53-year-old female presented with a painless, palpable lump within her left breast. A mammogram revealed a large encapsulated mass. Extended field-of-view sonography was utilized and demonstrated a large, hypoechoic, mildly compressible mass, which was suggestive of a lipoma.
Lipomas are nodules of mature adipose tissue. They are typically located within subcutaneous fat but may be located anywhere within the breast. Clinical presentation of lipomas is usually a nontender, soft, mobile, palpable mass. Lipomas can range in size from 2 to 20 cm.2 They rarely undergo malignant transformation and are not associated with an increased risk of developing breast cancer.
On mammography, large lipomas classically present entirely as a fat density and have a thin, peripheral water density capsule. Smaller lipomas may be difficult to distinguish from adjacent fibroglandular tissues if the water density capsule is not seen. Lipomas that demonstrate the classic benign appearance on mammography are classified as BIRADS category 2 and do not require sonographic evaluation. However, sonography is often used to evaluate palpable lesions and those associated with negative or nonspecific mammographic findings. Our patient presented with the palpable abnormality and therefore, sonography was performed.
There are 3 sonographic appearances of lipomas: (1) completely isoechoic to surrounding normal fat lobules; (2) mildly hyperechoic to nearby normal fat lobules; and (3) isoechoic compared to adjacent fat lobules and containing numerous thin, internal echogenic septa that course parallel to the skin line,2 as demonstrated by our case in Figure 13. In addition to the sonographic appearance, demonstrating the softness of the mass is crucial to the diagnosis of a lipoma. This can be accomplished by documenting a decrease in the anterior-posterior measurement of the mass with mild transducer pressure.
Case #6: Intramammary Lymph Node
A 35-year-old female patient presented for her baseline mammogram. A small density was noted within the superior lateral aspect of the left breast. Sonography demonstrated a hypoechoic nodule with an echogenic hilus, indicating an intramammary lymph node. Intramammary lymph nodes are quite common. They are frequently incidental findings detected with screening mammography.2 Documentation of a fatty hilus on mammography and sonography ensures the diagnosis of an intramammary lymph node (Figure 14). Color Doppler can also be used to demonstrate flow within the hilus to further confirm the diagnosis (Figure 15). Intramammary lymph nodes most often lie within the upper outer quadrants of the breast, but can be located within any quadrant, as well as the subareaolar area.2 Normal intramammary lymph nodes do not require any treatment and routine mammography is suggested.
Complex Presentations of Benign Pathologies
Some benign breast pathologies do not present with classic appearances and may even be suggestive of suspicious lesions. The 2 cases that follow provide examples of benign pathologies with initially suspicious findings that may be encountered in clinical practice.
Case #7: Breast Abscess
A 37-year-old female presented for imaging of a right palpable breast lump, after her physician had attempted to aspirate the mass because it was presumed to be an abscess. The breast was mildly swollen and warm to the touch in the areolar region. Sonography demonstrated an irregular, complex mass in the retroareolar region of the right breast (Figure 16).
Abscesses are frequent complications of mastitis or infected cysts. They may also result from trauma or infection. Infection may result from disruption of the skin with retrograde inflammatory progression.10
On mammography, an abscess may be imaged as an ill-defined, non-calcified mass. Abscesses are often not visible in imaging studies due to inadequate compression caused by breast tenderness.8 When viewed by ultrasound, abscesses commonly have thick walls and are oval or irregular in shape. They typically contain cystic and solid components, resulting in a complex appearance, and demonstrate acoustic enhancement. Effective treatment for abscesses includes antibiotic treatment or aspiration. Short-term interval examinations may be performed to confirm resolution.
Case #8: Fat Necrosis
A 57-year-old patient presented for a right diagnostic mammogram. Screening films from another facility demonstrated a focal abnormality in the medial aspect of the right breast. Straight medial lateral and craniocaudal mammography studies were performed. These views confirmed an asymmetric area of fibroglandular change, with slight architectural distortion in the superior medial aspect of the right breast (Figure 17). Sonography revealed a low-density mass with irregular margins, with associated shadowing and radial extensions (Figure 18). Spectral pulsed-wave Doppler demonstrated a high resistive index of 0.89 (Figure 19). A biopsy of the lesion confirmed a diagnosis of fat necrosis. No further treatment was performed after biopsy confirmation of a benign condition. Interestingly, this patient had no history of trauma or breast surgery.
Fat necrosis most commonly results from injury to breast fat.2 However, only 40% of patients with fat necrosis have a history of previous breast injury.10 Causes other than direct trauma or surgery include ischemia and chemical irritation.2 Fat necrosis can appear in 2 different ways on diagnostic imaging. One appearance of fat necrosis is characterized by an irregular, solid mass as a result of a fibrotic response to the injury, which may also be associated with skin thickening and nipple retraction. Cases of fat necrosis presenting with these imaging findings cannot be distinguished from a malignancy with mammography or sonography alone, and these cases require further follow-up with resection and biopsy. Alternatively, fat necrosis may also appear as a lipid collection without an inflammatory response.10
Miscellaneous Cases of Benign Breast Disease
Other presentations of benign breast disease with unique etiologies are also routinely encountered in clinical practice. The following cases represent 2 cases: mastitis in a patient who is breastfeeding and gynecomastia in a young male patient.
Case # 9: Mastitis During Breastfeeding
A 27-year-old patient presents with bilateral erythema and swollen breasts that were warm upon palpation. She had been breastfeeding her newborn for 6 weeks. Sonography was performed in lieu of mammography, revealing the presence of subcutaneous edema and no identifiable mass, suggesting a diagnosis of mastitis (Figure 20).
Mastitis is inflammation of the breast. It can be associated with lactation (puerperal) or other conditions, such as an infected cyst (nonpuerperal). On mammography, mastitis appears vague, demonstrating breast enlargement and edema as increased density. Therefore, sonography is typically the initial modality of choice in diagnosing suspected cases of mastitis. Edema affects all layers of the breast parenchyma in mastitis. The skin and subcutaneous fat become thickened and hyperechoic. In addition, the Cooper's ligaments may become more hypoechoic.2 Hyperemia may also be demonstrated with color Doppler. Treatment usually consists of antibiotic therapy. If not properly treated, an abscess may result that could require additional antibiotic therapy or even drainage.
Case #10: Gynecomastia in a Young Male
A 13-year-old male patient presented with a palpable mass. Because of the patient's age, only sonography was performed. Sonography revealed an irregular, hypoechoic area beneath the areola, which was highly suggestive of gynecomastia (Figure 21).
Benign breast disease can also occur in a male patient. Gynecomastia is a condition that results in male breast enlargement due to an abnormal proliferation of ductal tissue, glandular tissue, and stroma. Increased subcutaneous fat may also be noted. It is the most common disease process of the male breast and most common cause of palpable abnormalities.2 Due to the increased amount of testosterone present, puberty is the most common cause of gynecomastia, affecting approximately 60% of young males.2 Gynecomastia usually resolves spontaneously within a few months to a few years.
Technologists and other clinicians should note that another variation of the condition, pathologic gynecomastia, may be caused by mood altering medications, nutritional supplements, estrogenic medications, and steroids. This type of gynecomastia tends to present in young adults and middle-aged men.
In clinical practice, it is sometimes difficult to distinguish between gynecomastia and pseudogynecomastia. Pseudogynecomastia occurs in obese men. The breasts become enlarged simply because of fat deposition. In these cases, there is no proliferation of breast parenchyma. Mammography and sonography can easily document the difference between pseudogynecomastia and true gynecomastia. In cases of pseudogynecomastia, mammography will demonstrate a breast that is entirely fatty. True gynecomastia will present as a triangular area of water density tissue radiating out from the nipple into the breast tissues.2
The sonographic appearance of true gynecomastia varies with the histologic phase of the condition. A triangular area may also be noted ranging in echogenicity from hyperechoic to hypoechoic. Ductal structures converging toward the nipple may also be seen. Similar to the mammographic appearance, sonography demonstrates excess fatty tissue in cases of pseudogynecomastia.
Treatment of physiological gynecomastia is usually not necessary because the condition typically resolves spontaneously over time. Pathologic gynecomastia may require a change in medication to reduce hormone levels, or discontinued use of steroids.
Benign breast disease is commonly encountered but encompasses a range of pathologies with different presentations. Sonography is used in conjunction with mammography to diagnose breast lesions and rule out the possibility of malignancy. Although some benign lesions are straightforward in their sonographic diagnosis, others require additional short interval follow-up or biopsy. Sonographic studies are critical in clinical practice to reduce the need for unnecessary biopsy procedures and guide clinicians in determining the need for follow-up care. Radiologic technologists should therefore be familiar with the nature and sonographic appearance of benign breast lesions as they work with the rest of the clinical team to manage these common pathologies.
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Sonographic Features of Benign Breast Masses: A Case Review
|»||Comment From: janaholmes||» Posted on: 04/24/2009 16:16 PM|
|Great article! Very nice images and clear explanations.|
|»||Comment From: christed0208||» Posted on: 06/18/2009 8:37 AM|
|WELL WRITTEN GEORGE EKUKOLE (PHD, RDMS) DIAGNOSTIC HEALTH OF READING PA|
|»||Comment From: gayl||» Posted on: 06/18/2009 13:11 PM|
|very interesting. want more like this one|
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