Chapter 55

In parallel with the increasing use of mammographic screening and ultrasonography, nonpalpable breast lesions have been diagnosed with increasing frequency over the past 2 decades and at present constitute approximately 20% of all breast lesions.1

Nonpalpable lesions are a challenge to breast surgeons, because they must be precisely localized preoperatively and subsequently excised with clear margins and without excessive removal of breast tissue if the excision is merely diagnostic. Microcalcifications often found by screening mammography are frequently an early sign of neoplastic proliferation and must also be completely excised, an intervention that can forestall the development of infiltrating breast carcinoma.2 There are various methods for localizing these lesions: hooked wires, carbon particles, cutaneous markers, and large-molecular-weight colloids labeled with radioisotope.2 All are in current use. Needle localization is the most widely and frequently used method.3-5 The aim is to obtain accurate lesion localization and simultaneous surgical removal of the lesion with adequate margins.

Needle localization was first introduced in 1965 and became popular mainly thanks to refinement by Kopans and colleagues.6,7

### Needle Localization Procedure

A guide needle containing a stainless steel wire (Kopans wire) hooked at its distal end is inserted into the lesion under ultrasonic, mammographic, or magnetic resonance imaging (MRI) guidance. Ideally the guide needle should pass through the lesion and extend approximately 1 cm beyond. The wire must be long enough to protrude from the skin after insertion and withdrawal of the guide needle.8 Lesions revealed by ultrasound are best localized under ultrasonic control.9,10 Similarly, lesions detected only by MRI can now be localized using MRI guidance, and these procedures are becoming more refined.11 Once the correct position of the wire has been confirmed, the guide needle is carefully withdrawn. At this point, the hook in the wire reforms and anchors it in the tissue.8 More than 1 needle can be inserted into a single breast, for example to mark an extensive lesion by delimiting its borders. After localization, a 2-view mammogram (craniocaudal [CC] and mediolateral oblique [MLO]) is performed and sent to the operating room with the patient to document the location of the lesion and aid the surgeon with incision planning. The location of the target lesion within the breast is determined by estimating the distance from the nipple in both views; the CC view is used to determine whether the lesion lies medial or lateral to the nipple, and the MLO view is used to determine whether the lesion lies superior or inferior to the nipple. The depth of the lesion is also noted. Using the localization films in this manner allows the surgeon to estimate the location of the lesion in 3 dimensions and to place the surgical incision over the lesion itself, avoiding unnecessary dissection or tunneling through the breast if the entry site of the wire is in another quadrant of the ...

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