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Mammography:Additional Projections

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After reading the information presented, the reader should be able to:Identify the major anatomical structures of the female breast.Specify at least 3 reasons for taking additional projections.Define terms specific to mammography.Determine which supplemental views best demonstrate specific areas of interest.List in correct order the steps for positioning each supplemental view.Identify the appropriate uses of a BB. Determine the proper positioning for breasts that have implants. Tell from the localization map which projection helps localize a lesion.

This article describes additional positions for diagnostic mammography, the procedures and reasons for each view and problem-solving tips. Additional views in mammography can help to better demonstrate lesions and visualize more breast tissue.

Marty Ronish, PhD

Mammography:Additional Projections

When the 2 standard screening projections demonstrate a lesion needing further study, or when the initial screening

does not show enough breast tissue, fur-ther imaging is required. This course explains additional views that enable the mammographer and radiologist to visual-ize more breast tissue, see tissue from a different angle, magnify small areas, dif-ferentiate lesions from dense tissue, and detect any irregularities.

If additional views are indicated, the mammographer should explain to the patient that the need for extra films does not necessarily mean there is a problem; the extra views show breast tissue in more detail. When additional views reveal a problem, the mammographer provides empathy and support to the patient and works closely with the radiologist.

Practicing mammographers know an academic explanation of additional views is no substitute for the understanding that

comes from day-to-day experience. The mammographer must be resourceful and creative to find whatever position or angle produces the best possible image.

AnatomyThe mammographer must understand

the anatomy of the breast to position and compress the breast properly. The image should show as much tissue as possible. Expert processing and dedicated equip-ment cannot be effective if positioning is poor. At worst, such mistakes can yield a false negative, and important pathologies might be missed.1

The base of the breast extends from the second to the sixth rib in the midclavicu-lar line over the pectoralis major muscle. The glandular tissue always spreads far-ther than the gross outline of the breast. A long, tongue-like process of breast tissue, the axillary appendage or tail of Spence, extends from the main mass up the ante-rior axillary line toward and even into the

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and extralobular ducts), leading into lobules. Lobules are made up of intralobular ducts, terminal ducts (ductules) and, during lactation, several small saccular glands, or acini, which are the milk-producing units of the breast.

The lobule is the functional unit of the mammary gland. Every glandular lobe is divided into 20 to 40 lob-ules, each about 1mm to 2 mm in diameter. Standard terminology designates the lobule and the duct leading into it as the terminal ductal lobular unit (TDLU).1,2,3 On a mammographic image the TDLUs appear as tiny overlapping densities. Most lesions, benign or malignant, appear in these tissues.

During pregnancy and lactation, the terminal ducts and acini, which start out as buds during puberty,4 increase in number and size. Mammograms are taken during this period only if the patient experiences symp-toms, and then only after the breast has been emptied of milk for a clearer image.2 After lactation ceases, lobules and small ducts atrophy and gradually are replaced by fat. Because fat is more radiolucent than glandular tissue, mammographic images of postlactating women tend to appear less dense. This is important because any growth or new tissue in these glandular regions can indicate the presence of malignancy.2

Why Take Additional Views?Telling a patient that additional films are neces-

sary can cause a great deal of worry and anxiety. Nevertheless, the reasons for taking additional projec-tions are important. By taking the time to explain these reasons, the mammographer or radiologist can alleviate some of the fear while also educating the patient.

The radiologist will request additional views if the standard projections fail to show a portion of the breast tissue. Additional films may be necessary if the patient is large-breasted or obese, very small-breasted, kyphotic, barrel-chested, male, has breast tissue extending far into the axilla, or has had a mastectomy, lumpectomy, pace-maker, chest surgery, or implants.

Sometimes overlapping tissue in the breast appears on film as a suspicious-looking mass. This mass may show up on 1 standard view but not the other, so the radiologist will request additional images to determine whether it is a radiographic distortion or a true mass. Overlap also can obscure the clarity of tissues behind it; an underlying lesion may be overlooked when it is

axilla. This glandular tissue is of considerable impor-tance, because it is a common site of benign or malignant abnormalities that often are mistaken for pathology of the axillary lymph nodes. On mammograms, the axillary tail of breast tissue usually is seen best in the mediolat-eral oblique projection.

Histologically, the female breast has 15 to 20 lobes of glandular tissue with associated ducts, called the lactifer-ous ducts, extending to orifices at the nipple (see Figure 1). Each lactiferous duct enlarges immediately behind the areola to form a lactiferous sinus, in which milk and other secretions can accumulate. Beyond the lactiferous sinuses the ducts branch and rebranch (the excretory

Figure 1. Anatomy of the breast. Illustration by Yvonne Walston, MA, CMI., ©1995 Creative Imagery Inc. Albuquerque, NM.