Difficulties In Stereotactic Breast Biopsies

It is important for the physician to anticipate that some patients and some lesions will be difficult for obtaining biopsy specimens. Certain lesion characteristics, such as low-density nodules, faint or nonclustered microcalcifications, or vague asymmetric densities, may be difficult to visualize with digital imaging despite postprocessing features. The position of certain lesions, such as those that are very superficial, those against the chest wall, or those in the axillary tail of the breast, may require innovative positioning by the experienced technologist. However, some lesions may be inaccessible. It is essential that the physician be able to recognize and correct for targeting errors (Figures 4-14A to 4-14C). Certain patient characteristics will interfere with the success of a stereo-tactic breast biopsy. Patients with neurologic or musculoskeletal conditions may not tolerate positioning on the stereotactic table. Patients that are coughing because of an acute or chronic respiratory condition will increase breast motion and lesion movement, which may interfere with accurate targeting. Patients with a high level of anxiety, especially those suffering from claustrophobia or agoraphobia, may require sedation. As any biopsy has the potential for bleeding complications, those patients with a history of bleeding abnormalities or who are taking anticoagulants will require correction prior to biopsy. The small or ptotic breast creates one of the most common difficulties in stereotactic breast biopsy. A breast that flattens to a marginal thickness in compression may lead to "stroke margin problems." The stroke margin is defined as the distance in millimeters from the postfired biopsy needle/probe to the back of the breast or the rear image receptor. The stroke margin must be greater than zero on the Lorad Stereoguide™ system or greater than a positive 4 mm on the Fischer Mammotest™ table (Figure 4-15). When a breast is very thin, or the lesion is more posteriorly positioned, a negative stroke margin may be encountered. This situation will result in the biopsy needle or probe striking the rear image receptor and piercing the back of the patient's breast skin.

Figure 4-13. Postprocedure images after six samples with the vacuum-assisted device illustrated the air-contrast cavity and the majority of calcifications removed.
Pre Post Fire Error Biopsy

X Axis Targeting Errors

Y Axis Targeting Errors

Stereo Images

IDQl J

Pre Post Fire Error Biopsy

Figure 4-14. A, Correct pre- and postfire needle/probe alignment with the lesion result in favorable tissue sampling. B, An "X" targeting error will result in the needle/ probe being off to one side of the lesion. A "Y" targeting error will result in the needle/ probe being above or below the lesion. C, A "Z" axis targeting error will illustrate the needle/probe being too far in front or too far past the lesion. All three targeting errors become less important with the vacuum-assisted device.

Figure 4-14. A, Correct pre- and postfire needle/probe alignment with the lesion result in favorable tissue sampling. B, An "X" targeting error will result in the needle/ probe being off to one side of the lesion. A "Y" targeting error will result in the needle/ probe being above or below the lesion. C, A "Z" axis targeting error will illustrate the needle/probe being too far in front or too far past the lesion. All three targeting errors become less important with the vacuum-assisted device.

Adequate Stroke Margin

Stroke (mm)

Pre - Fire

Biopsy—* compression piale

Pre - Fire

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Do Not Panic

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