Objectives

• Describe the sonographic anatomy of the breast

• Define the breast parenchymal patterns

• List the incidence, risk factors, and reproducible variables in breast disease

• Name the primary and secondary signs of breast cancer

• List the sonographic descriptive factors in the breast evaluation

• Describe the sonographic criteria for a simple cyst of the breast

• Describe the sonographic appearance of a breast fibroadenoma

• List the characteristics of malignant breast lesions

Introduction

The evaluation of the breast with diagnostic ultrasound has been a topic of continued interest of clinicians and researchers involved in the diagnosis and treatment of breast disease for the past four decades. Initial studies in the early fifties with breast ultrasound were pioneered by Wild and Reid. Howry and Bliss joined in the research shortly thereafter. However this research in ultrasound became overshadowed by the developments in mammography as a gold standard for breast screening. The purpose of this article is to present an overview of the etiology, risk factors, clinical signs and symptoms, and diseases that breast disease may present to the sonographer.

Key Statistics About Breast Cancer

• Breast cancer is the second leading cause of cancer death in women.

• The American Cancer Society estimates that in 1998 about 178,700 new cases of invasive breast cancer will be diagnosed among women in the United States.

• The breast cancer incidence rate increased by 4% per year during the 1980s but during the past few years, incidence has leveled off.

• In 1998, there will be about 43,900 deaths from breast cancer in the United States.

• The breast cancer mortality rate has been decreasing during the past few years.

• Increased screening of women, leading to detection of cancers at an earlier stage. More effective treatments are most likely responsible for lowering the breast cancer mortality rate.

Background

During the sixties, a small number of individual investigators throughout the world began to study the possibility of ultrasound visualization for breast examination. Interestingly enough, these early techniques used to "couple the sound" with the breast included the use of a water bath, compression of the breast with a plastic window, or direct contact scanning. Direct realtime scanning of the breast with a very high frequency transducer is the preferred method used today to examine the breast tissue. Improvements in transducer design and tissue processing techniques have led to improvement of the breast tissue texture in ultrasound diagnosis.

Early investigators in breast disease attempted to use ultrasound as a massive screening tool with the intent of replacing the high radiation dose rendered by older mammographic systems. The "automated" water path system was developed in an attempt to efficiently screen large numbers of women of all ages.

In the seventies the Japanese applied color ultrasonography and C-mode (coronal) imaging to examine the breast. With this development came improved gray scale and range resolution of the breast tissue. In the mid-seventies, the Australian group developed the large diameter, long focal length transducers to scan the breasts suspended in a waterbath. Problems were encountered in the region deep to the nipple-aerola and the outer edges of the breast where total reflection of the sound beam occurred.

In the seventies Jellins, et.al. suggested that ultrasound visualization should be the initial imaging examination for symptomatic patients under 30 years of age. This reasoning was based on the facts that: 1) a large number of women of that age have dense breasts, which are not well imaged by mammography; 2) ionizing radiation should be avoided in younger subjects; 3) if a mass is found, ultrasound can determine whether it is cystic or solid; 4) if the mass is benign, ultrasound can be used to follow the patient's progress. These investigators diagnosed cystic structures with a 98% accuracy and detected cysts as small as 2mm in diameter.

Further investigation revealed that compression of the breast tissue improved the resolution in some of the more difficult patients. Transducer designs were finally based on imaging a compressed breast. The most important of these were:

• structures in the nipple-areola region which are not well imaged if the breast is uncompressed can be adequately scanned.

• the flattening of the breast surface by the applied compression solves the critical angle problem.

• for a single focus transducer, it allows attainment of a relatively narrow beamwidth for the full depth of the breast,

• high frequencies, yielding better range and lateral resolution, can be applied without sacrificing adequate imaging of deep structures,

• as a consequence of the smaller tissue depth, there is less spectral shift to lower frequencies as the sound penetrates the deeper aspects of the breast and thus a sharper focus in these regions.

For single-focus transducers, only three transducer design parameters control range, lateral resolution, and depth of field: 1) the diameter, 2) the focal length, and 3) the frequency.

The difficulty of the waterpath ultrasound arose in the interpretation of the images. Many clinicians did not acquire the proficiency to interpret the breast images accurately. It was difficult to separate areas of fat from abnormal breast lesions. The amount of images it took to adequately scan each breast at small millimeter increments was incredible, and difficult to interpret because of the fatty composition of many breasts.

In the meantime, ultrasound companies had developed improved resolution and transducer design with realtime equipment to such a point that it became more efficient to place the transducer directly on the breast and determine if the lesion was cystic or solid. Mammography equipment and film development was also perfected to reduce the amount of radiation exposure and improve the image quality. Therefore, most laboratories today still consider the mammogram radiography as the gold standard for diagnosing breast disease. Ultrasound is utilized to further characterize the texture of the mass after it is located on the mammogram.

Sonographic Anatomy Of The Breast

Ultrasound has the ability to distinguish soft tissue layers within the breast parenchyma. There can be considerable variation in the image depending upon the ratio of the parenchymal to stromal elements in the area of the breast that is being imaged. The parenchyma includes the lactiferous ducts and alveoli of the breast as well as the intralobular connective tissue. The stromal or supporting tissues can be divided into fat and dense connective tissue.

In a normal, premenstrual breast, these areas are demonstrated:

• subcutaneous fat

• fibroglandular tissue

• lactiferous ducts

• retromammary space

• muscle layers

• ribs

The patient is examined lying supine or in a slight decubitus position with her arm elevated behind her head. A circular "clock" pattern is performed beginning at the nipple/areola area with gradual clockwise movement making a spiral pathway until the chest wall is reached. Likewise, if a lesion is detected, it is noted in it's "clock" position on the breast (i.e., mass at 1:00, 3:00, etc.)

The basic principle of ultrasound relies on the fact that the amplitude of the echo generated by the ultrasound reflections at an interface depends upon the difference in acoustic impedance between the two tissues, fat/dense connective tissue to strongly echogenic as compared to the fat/parenchyma interfaces or dense connective tissue/ parenchymal interfaces. Sonography demonstrates that fatty tissue has a relatively low acoustic impedance and sparse low-level echoes in contrast to the high-level intensity echoes of fibrous tissue, which has a relatively high acoustic impedance. The proportions of parenchymal and stromal elements vary considerably within the breast and therefore, careful interpretation of the images must consider this aspect of anatomy.

Skin. The skin is imaged as a thick echogenic line of tissue. The thickness of this line depends upon the degree of compression with the transducer.

Subcutaneous Fat. The subcutaneous fat lies deep to the skin. The amount of fat varies tremendously with age and parity of the patient. Usually in the young woman there is little or no subcutaneous fat, the amount normally increases with age and parity. Multiple distinct fat lobules are often identified separated by highly echogenic connective tissue ligaments (Cooper's ligaments). The orderly orientation of fat lobules is often seen best when scanning is being performed in the longitudinal plane (generally because of the lie of the fat lobules and connective tissue ligaments). Sometimes these dense supporting ligaments cause attenuation shadowing, making it difficult to image the posterior structures with ultrasound. Moving the transducer with a slight angulation usually allows one to avoid the shadowing and image the structures beyond this ligament.

Fibroglandular Layer. The fibroglandular (parenchymal) layer lies below the subcutaneous fatty layers. Separating these two layers is the highly echogenic band of tissue which represents the superficial fascia. The parenchymal layer consists of the ducts and alveoli, including the intralobular connective tissue. Some of the dense intralobular connective tissue, which is part of the stromal tissue component, may be difficult to differentiate from the remainder of the parenchyma because of similar imaging characteristics. Deep to the fibroglandular tissue is the deep fasica, which has an appearance similar to that of the superficial fascia.

Retromammary Layer. The retromammary layer lies between the deep connective tissue plane and the fascia of the uderlying muscle. This layer predominantly contains fat lobules which are smaller than those found in the subcutaneous layer. Connective tissue ligaments are not usually seen in this layer because they are thinner than in the subcutaneous layer.

Pectoralis Muscles. The pectoralis major and minor muscles are usually easily demonstrated depending on the area of the breast that is being scanned. They are imaged as structures of relatively low echogenicity running deep in the breast above the ribs and parallel to the skin. The structures are more prominent in small-breasted women and may be quite large in athletic individuals. The muscles are best imaged in the transverse plane.

Ribs. The ribs form the ventral aspect of the thoracic cage over which the breasts lie. They are composed of bone laterally and cartilage medially. When ultrasound scans are performed over the lateral aspect of the breast, the ribs are seen as highly attenuating structures interposed by the intercostal muscles. Medially, the cartilage is visualized as oval masses with sparse internal echoes. The deep connective tissue plane and muscle groups which lie superficial to these structures must be identified so the "solid" reflections from the ribs are not mistaken as breast lesions.

Nipple and Areola. The nipple and areola are slightly more attenuating than the rest of the breast. These structures show attenuation shadowing of the ultrasound beam, in part because of the dense connective tissue within the nipple itself and in part because of the columns of connective tissue surrounding the lactiferous ducts. If a mass is suspected posterior to this area, the transducer is moved away from the areola area and angled towards the area of interest.

Lactiferous Ducts. The lactiferous ducts are easily seen on most scans, especially when they are dilated. A typical breast is composed of 15-20 lobules which are drained by a network of ducts. These ducts branch into the peripheral breast tissue and join in the subareolar region to form approximately 15-20 ducts which drain into the nipple. The lactiferous ducts are usually collapsed in the nonlactating breast and measure under 2mm. At the sinus level in the subareolar region the ducts may have a potential diameter of 8mm. In the periphery of the breast, a diameter of 2-4mm is normal in the lactating breast. Surrounding the subareolar ducts are varying amounts of fibrosis, which accentuate the degree of nipple shadowing observed. The terminal ductal lobular unit is the site of fibroadenoma, epithelial cyst, ductal and lobular carcinoma in situ, infiltrating ductal and lobular carcinoma adenosis, epithiosis, and apocrine metaplasia.

Breast Parenchymal Patterns

In the young nonlactating breast, the tissue is primarily composed of fibroglandular tissue with little or no subcutaneous fat. With increasing age and parity, fat is deposited in both the subcutaneous and retromammary layers.

During pregnancy there is a substantial increase in glandular tissue in the breast. The resultant image on ultrasound demonstrates a finely granular echo pattern with little subcutaneous fat. The subcutaneous and retromammary fat layers are compressed by the glandular tissue and are decreased in size. Late in pregnancy and during lactation, the lactiferous ducts increase in size and number with resultant duct dilatation throughout most of the breast tissue.

Cyclic breast changes may occur with each menstrual cycle. Ultrasound may image mild duct dilation during the period between ovulation and menstration. In most normal women, no significant changes are noted.

The postmenopausal breast demonstrates varying amounts of fibrous tissue interspersed among predominantly fatty tissue. With increasing age, there is normal regression of the glandular tissue with subsequent replacement by fat.

Breast ultrasound is used as the initial method for evaluating the following symptomatic patients:

• The young patient under 30 years of age.

• The pregnant patient.

• Follow-up of patients with fibrocystic disease (3-6 month intervals).

Breast ultrasound is used as a complementary examination to mammography in the following situations:

• Evaluation of dense breast tissue.

• Evaluation of a mass demonstrated on mammography.

• Guidance of biopsy needle or needle localization (see cyst aspiration image)

Breast cancer can lie hidden from mammography in women with dense breast tissue, and thus the role of ultrasound is implemented to evaluate the texture and anatomical structures within the breast. Women most likely to have dense breasts are younger, premenopausal women and postmenopausal women who are taking hormone replacement therapy.

Epidemiology

Incidence. There are 2-5 new breast cancers per 1,000 women each year. Breast cancer comprises 25% of all female malignancies. The age is 2% occur in women under 30 years, 15% occur in women under 40 years, and the majority, 85% occurs in women over 30 years.

Risk Factors. Significant risk increases with age. White females over forty are more affected than Afro-American females. Upper class females are more affected than lower social class females; and unmarried are affected more than married women.

Reproductive Variables. The risk factor increases in the nulliparous, first full term pregnancy after the age of 35, early age at menarche (<12 years), late age at menopause (>55 years), and in patients with early bilateral oophorectomy.

In patients with multiple primary cancer, the risk increases for developing cancer in the contralateral breast. The risk also increases after ovarian and endometrial cancer. The family history is significant in that the risk doubles if the mother and sister both had breast cancer. Breast cancer affects successive generations ten years earlier.

Differential Diagnosis

There are many characteristics that help the sonographer determine the sonographic image of the breast to provide a differential diagnosis for the clinician. These characteristics include: size of the lesion, shape, margins of the lesion, location, number of lesions, interval change in lesion, nipple discharge, skin changes, and patient risk factors.

Size. A well defined lesion under 1cm has a very low risk for cancer.

Shape. There is an increased probability of malignancy as the shape of the mass changes. A round lesion is more often associated with a benign process; an irregular shaped lesion is often malignant.

Margin. The margins surrounding the lesion may be very helpful to define the characteristics of the mass. A well circumscribed mass is most likely benign, (4% risk of malignancy). On ultrasound, a well defined mass is either a cyst (if the internal structure is anechoic- "without echoes" and has increased through transmission) or a fibroadenoma. Other well defined masses may include a papilloma, galactocele, and sebaceous cyst.

A microlobulated mass has an increased risk of cancer. If the margin is obscured, infiltrative cancer should be considered. When the margin becomes irregular and ill-defined, the probability of cancer increases. Malignant masses may include medullary, mucinous, intracystic, or papillary carcinoma. Other rare conditions include invasive ductal carcinoma and metastases from melanoma, lymphoma, leukemia, lung cancer, or hypernephroma.

Calcifications are not well detected on ultrasound unless they are at least lmm in diameter. When seen the calcifications cause an acoustic shadow posterior to the lesion.

Location. The upper outer quadrant of the breast is the most typical location for intrammamary lymph nodes while sebaceous cysts are found in the subcutaneous tissue layer. The location of masses is specific to the breast in this order:

Upper outer quadrant 54%
Upper inner quadrant 14%
Lower outer quadrant 10%
Lower inner quadrant 7%
Retroareolar 15%

Number. Identical multiple lesions decreases the risk of malignancy; it is usually associated with fibrocystic changes in the breast.

Interval Change. A mass that has changed in shape or size should be localized for a biopsy.

Nipple Changes. A nipple retraction may be relative to inflammation or edema of the periareolar tissue, congenital defect, or acquired (carcinoma or ductal ectasia). A nipple discharge may be bloody (most common is intraductal papilloma) or secondary to a lactating breast.

Skin Thickening. The normal skin thickness should measure less than 3mm. The skin normally thickens in the lower dependent area of the breast. Localized thickening may be secondary to trauma (biopsy), carcinoma, abscess formation, mastitis, or dermatologic conditions.

Patient Risk Factors

• Increasing age increases risk for malignancy

• Positive family history of breast cancer

• Primary cancer elsewhere in body

Ultrasound Evaluation Of The Breast

Ultrasound may be used as a target exam to analyze the texture of the lump either found by palpation or mammography. In addition, whole breast ultrasound may be utilized to detect silicone leakage, image the dense breast, to define the presence of metatastic disease, in the pregnant patient, or in patients who refuse mammography. As a tool for the interventionalist, ultrasound may be used as an aid in cyst aspiration, core biopsy procedures, or abscess drainage.

"Sonography improves the specificity of the diagnosis of the majority of nodules and allows a better definition of both local and regional staging in nodular and diffuse conditions. Color Doppler and contrast media are increasing ultrasound specificity and are particularly useful in evaluating vascularity during therapies. Benign conditions like inflammations, traumas, and duct ectasia are very useful for ultrasound diagnosis." (Rizzatto and Chersevani)

Breast Cyst. Breast cysts are the most common single cause of breast lumps in women between 35-50 years of age. A cyst occurs when the fluid can't be absorbed due to obstruction of extralobular terminal ducts by fibrosis or intraductal epithelial proliferation. The sonographer should look for the number, size, and internal characteristics of the mass to determine if it is a cyst. A cyst is usually well defined, round or oval, solitary or multiple. The size may change with the menstrual cycle. (See breast cyst image)





Simple Cyst

• anechoic

• well-marginated

• round, ovoid, or lobulated

• solitary or multiple

• well-defined posterior wall

• acoustic enhancement

Complex Cyst. A complex cyst shows low-level internal echoes/ fluid-debris level. These internal echoes may be caused by floating cholesteral crystals, pus, blood, or milk of calcium crystals. The transmission is usually increased as in a simple cyst. (see complex breast mass)

Chronic Abscess Of The Breast. Clinical symptoms include fever, pain, tenderness to touch, increased white blood count. The most common location is in the central to subareolar area. An abscess may range from somewhat ill-defined to well-defined, anechoic to low-level echoes, with posterior enhancement. (see breast abscess image)

Cystosarcoma Phyllodes. This condition is a giant fibroadenoma, occurring in 3% of all fibroadenomas. It usually occurs in the older female as a rapidly enlarging breast mass. The mass is very large, sometimes comprising the entire breast. A very small percentage may become malignant. On ultrasound the margins are well defined with a hypoechoic texture and decreased through transmission. Internal echoes may be fine or coarse with a variable effect on posterior echoes.

Fat Necrosis. Fat necrosis occurs in a very small percentage of breast biopsies, post-surgery, or after radiation treatments. It may be found anywhere however is more common in the areolar region or near the biopsy site. The appearance is a firm, slightly fixed mass with skin retraction in half of the cases. The mass may show calcifications. On ultrasound, it appears as hypoechoic to anechoic with ill-defined margins. Acoustic shadow may or may not be present.

	Duct Ectasia. This lesion has a variable appearance; it may be elongated and filled with fluid. (see ductal cyst image) Old cellular debris may appear as hypoechoic on ultrasound, however the "tubular" appearance is more typical.
	Fibroadenoma. This benign mass is an estrogen induced tumor that forms in adolescence. The onset of pregnancy and hormone replacement therapy are growth stimulants. It is the third most common breast lesion after fibrocystic disease and carcinoma. A fibroadenoma is the most common benign tumor in women of child-bearing age. The mass presents as a firm, smooth, oval shaped, well-marginated (sometimes lobulated), freely movable mass. It is rarely tender or painful. The size is under 5cm, the number is multiple in 10-20% and bilateral in 4%. Calcifications may occur. On ultrasound, the texture is usually homogenous and hypoechoic with low-level echoes. (see fibroadenoma image) In a small number of patients, the mass may appear complex, hyperechoic, or isoechoic. The solid nature of the mass prevents acoustic transmission. The differential diagnosis may include medullary, mucinous, or papillary carcinoma.
	Fibrocystic Changes. This condition is found in 72% of the screening population over 55 years of age. The cause is an exaggeration of normal cyclical proliferation and involution of the breast with production and incomplete absorption of fluid by apocrine cells. Clinical symptoms include fullness, tenderness, and pain that varies with the menstrual cycle. There may be palpable nodules and thickening within the breast. The cystic changes include round to ovid cysts with smooth margins. They may be lobulated or multilocular. These changes are well defined on ultrasound. See fibrocystic image)

Adenosis. This condition includes hyperplasia and hypertrophy of the glandular elements within the breast. The lobules show an increase in size and on ultrasound appear as isoechoic to mildly isochoic as compared with fat.

Hematoma Of The Breast. Causes of hematoma may be from surgery or biopsy, blunt trauma, coagulopathy, or anticoagulant therapy. A hematoma usually appears as a well-defined mass with tiny low level echoes floating within (red blood cells). Through transmission is good.

Hamartoma. This lesion is rarely seen; the mean age is 45 years. The mass is soft and nonpalpable in 60% of patients. It appears in the retroareolar and upper outer quadrant in 65% of patients. A hamartoma is round or ovoid, well-circumscribed, and less than 3 cm in size. It may contain calcifications. Ultrasound findings have shown a harmartoma to contain fibrous elements that may be specular in their reflections with hypoechoic texture. The mass is encapsulated and distinct from surround tissue.

Lipoma. This mass is a solitary, slow growing lesion that presents in the middle aged and postmenapausal female. The patient is usually asymptotic. The ultrasound appearance would be similar to normal fatty lobules found in a normal breast. The lipoma is hypoechoic in texture. The sound is attenuated and scattered similar to normal subcutaneous and intrammary fat.

Characteristics Of Malignant Lesions

Hypoechoic Lesions with Ill-Defined Borders. Lesions with ill-defined margins are more likely to be malignant. If the anterior margin of the lesion is somewhat triangular, malignancy should be suspected. (Kopans)

Lesions that Produce Posterior Acoustic Shadowing. Acoustical shadowing is not always indicative of malignancy. Cooper's ligaments may shadow because of refraction from the steep angle of incidence. Fibrosis or a previous surgical scar tissue may produce an acoustic shadow. These fibrotic areas are particularly seen in the upper outer quadrant. Fibrocystic breast tissue with pericystic fibrosis may also cause shadowing.

Ultrasound Appearance Of Malignant Disease Of The Breast

• hypoechoic

• irregularly marginated (especially anterior margin)

• heterogeneous internal echoes

• acoustic shadowing

Lymphoma. A small percentage of patients have lymphoma as a primary condition, most have metastatic disease secondary to lymphoma. It usually is found in the older patient with a right side predominance. The mass varies from well defined to infiltrative with poorly defined borders. On ultrasound the texture is hypo to isoechoic without through transmission. Axillary nodes are present in 35% of patients.

Metastases To The Breast. There is a 1% incidence of metastases to the breast from primary tumors that include malignant melanoma, ovarian carcinoma, and leukemia/lymphoma. The mean age affected is 45 years. The mass is usually solitary and well circumscribed and appears in the upper outer quadrant. One fourth of the patients have skin adherence and 40% have axillary node involvement.

Sarcoma and Angiosarcoma. A sarcoma is a rare malignant mammary lesion occuring in the middle aged female. The growth is rapid. Borders are well-defined with lobulations.

Angiosarcoma is a highly malignant vascular breast tumor that affects females in the third to fourth decade of life. The mass gradually enlarges; its borders are ill-defined and there is skin thickening with nipple retraction. On ultrasound angiosarcoma presents as a well-defined multilobulated hypoechoic mass with hyperechoic areas as a result of hemorrhage.

Noninvasive Breast Cancer. This type of cancer accounts for 15% of all cancers. It occurs when there is a malignant transformation of epithelial cells lining the mammary ducts and lobules confined within the boundaries of the basement membrane.

Noninvasive Breast Cancer

• ductal carcinoma in situ,

• lobular carcinoma in situ

• intracystic papillary carcinoma in situ.

Ductal carcinoma in situ. This is the most common noninvasive carcinoma. It occurs in postmenapausal women over 55 years old. The mass may persist for years without a palpable abnormality. Therefore, when the mass is noted, it is usually large enough to feel by palpation; nipple discharge may be present as well as microcalcifications.

Lobular carcinoma in situ. This disease arises in the epithelium of the blunt ducts of the mammary lobules. It comprises about one fourth of the noninvasive cancers, with an increased incidence during the reproductive years. It may present as a noncalcified mass, or with calcifications and a palpable mass. It may also occur on the contralateral breast.

Intracystic papillary carcinoma in situ. This cancer is rare and affects middle aged females with the average age 51 years. The mass is well circumscribed and freely moveable. Bloody fluid is obtained with aspiration. Ultrasound findings show a solid well-defined mass.

Invasive Breast Carcinoma. This type of malignancy accounts for the majority of breast cancers in 85% of the population.

Invasive Breast Cancer

• Infiltrating/invasive ductal carcinoma (65%)

• Invasive lobular carcinoma (8-13%)

• Tubular carcinoma (6-8%)

• Medullary carcinoma (2%)

• Mucinous carcnimoa (2%)

• Papillary carcinoma (2-4%)

Infiltrating/ invasive ductal carcinoma. Most of these patients present with a palpable mass (70%), spiculations (36%), and malignant calcifications (45-60%).

Invasive lobular carcinoma. This is the second most common type of breast cancer (30-50%). At least 30-50% of patients will develop a second primary in the same or opposite breast within 20 years. It is the most frequently missed cancer as it is difficult to detect on mammography and by clinical examination. Clinical findings may show architectural distortion, thickening of fibrous septa, spiculations, poorly defined borders, microcalcifications, and skin/ nipple retraction.

Tubular carcinoma. This cancer is a well differentiated form of ductal carcinoma occurring in the middle aged female with a positive family history. It is associated with lublar carcinoma in situ in 40% of patients.

Medullary carcinoma. This is the fastest growing breast carcinoma seen in the middle aged female. The mass is well circumscribed with a nodular architecture and lobulated contour. In larger tumors, a central necrosis may be seen. On ultrasound the mass appears hypoechoic with some through transmission if there is central cystic necrosis and indeterminate borders. A differential diagnosis would be fibroadenoma.

Mucinous colloid carcinoma. This rare tumor appears in older women and shows a slow growth pattern.

Papillary carcinoma. Most women present with a palpable mass with a quarter showing nipple discharge. The mass is usually solitary with well-circumscribed borders. More than half will show microcalcifications. There is a 90% five year survival rate after a mastectomy.

Conclusion

Ultrasound evaluation of the breast has made a contribution to the field of women's health diagnosis in offering additional information for the clinician. The improvements in near field resolution, high frequency transducers, and image processing has enabled the sonographer to clearly distinguish the normal breast pattern from the abnormal disruption secondary to a mass formation. Ultrasound offers the patient additional information as an alternative to biopsy of all lesions detected on mammography. Continued research in color Doppler and 3-D evaluation of the breast should provide additional information for the clinician.

Bibliography

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Hagen-Ansert, Sandra L., TEXTBOOK OF DIAGNOSTIC ULTRASONOGRAPHY, 4th ED., Mosby, St. Louis, 1995.

Harper, P. "Ultrasound anatomy of the breast" in Ultrasound Mammography, University Park Press, Baltimore, 1985. pp. 43-51.

Howry, D.H., Scott, D.A., and Bliss, W.R. "The ultrasonic visualization of carcinoma of the breast and other soft tissue structures" in Cancer 7: 354-358, 1954.

Jellins, J., Kossoff, G., Buddee, F.W., and Reeve, T.S. "Ultrasonic visualization of the breast" in Med. J. Aust. 1: 305, 1971.

Kelly-Fry, E. "Influences on the development of ultrasound pulse-echo breast instrumentation in the United States" in Ultrasound Mammography, P. Harper, Editor. University Park Press, Baltimore, 1985. pp. 1-21.

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