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Nonconventional Options for Tumor Localization in Breast and Axillary Lymph Nodes: A Pictorial How-To
Address for correspondence: Dr. Asha A Bhatt, Department of Radiology, Mayo Clinic, 200 1st, SW Rochester, Minnesota 55905, USA. E-mail: bhatt.asha@mayo.edu
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Abstract
Preoperative localization of breast malignancies using traditional ultrasound and digital techniques can be challenging, particularly after neoadjuvant chemotherapy when the target is not conspicuous. The purpose of this paper is to pictorially present nontraditional techniques that have been helpful in preoperative localization before surgery. We will discuss techniques for breast lesion localization using computed tomography (CT) and magnetic resonance imaging (MRI) as well as axillary lymph node localization using tomosynthesis, CT, and MRI.
Keywords
Computed tomography
localization
magnetic resonance imaging
tomosynthesis
INTRODUCTION
Malignancy in the breast or metastatic lymph nodes (LNs) is commonly localized before surgery to assist the surgeon in locating the site of disease for operative removal.[12] Ultrasound guidance is generally the preferred method to localize malignancy in the breast or to localize metastatic axillary lymphadenopathy when the target is visible sonographically. Like biopsies, an ultrasound-guided localization is more comfortable for the patient as the breast is not in compression during this procedure. A digital localization technique is also commonly used for localization of lesions in the breast when the tumor is not well-visualized sonographically. In such cases, the clip marking the site of disease is mammographically visible for digital localization before surgery. However, not infrequently, preoperative localization of the tumor and/or the clip marking the site of disease cannot be performed, especially after neoadjuvant therapy (NAT), using the above-mentioned traditional ultrasound or digital methods. The purpose of this paper is to describe nontraditional methods for localization of tumor within the breast or axillary LNs in difficult cases when traditional techniques fail. The techniques presented are based on well-established cross-sectional (computed tomography [CT] and magnetic resonance imaging [MRI]) interventional methods.[3456789] The translation of these techniques to breast interventional techniques is highlighted here.
Computed tomography guidance
CT guidance for localization in the axilla is an option if the clip is not visible on ultrasound or mammogram. Axillary clips can sometimes be difficult to visualize on ultrasound, especially if the LN has normalized in size after NAT. LNs situated high in the axilla also may not be included in the field of view on digital mammogram. In such cases, a limited noncontrast CT of the axillary region can be obtained with the patient in the supine position. Most clips are visualized on CT as metallic artifact, making it easy to identify the clip within a normal size metastatic LN seen after NAT on CT. Once the metastatic LN is identified, it can be localized using CT fluoroscopy, and a seed or wire can be deployed within the metastatic LN as demonstrated in Figures 1a–f. The method is similar to CT-guided seed localization in the breast as illustrated in Figures 2a–e.
Magnetic resonance imaging guidance
MRI guidance for clip placement or localization is much less frequent, and it is usually considered when the initial target was only visualized by MRI.[1011] For MRI-guided approaches, the patient is scanned in the conventional prone position similar to MRI breast biopsies. Intravenous gadolinium-based contrast agent may or may not be needed to locate the target lesion in the breast.
Clip placement and localization in the breast under magnetic resonance imaging guidance
There are times when the lesion/clip cannot be visualized by ultrasound, and the clip cannot be localized using a digital technique due to clip migration after biopsy. When the initial target is only visualized with MRI, MRI-guided clip placement may be utilized for accurate localization for subsequent digital localization at a different time. For MRI-guided clip placement and localization, the patient is placed in a prone position with the breast compressed, similar to performing a breast biopsy. A noncontrast sequence is initially performed to localize the region of tumor. Once the appropriate region of interest is in the field of view, contrast is administered to identify the tumor, and clip placement which can then subsequently be localized with digital mammogram technique. An MRI-guided clip placement is illustrated in Figures 3a–e.
Localization under MRI guidance can be performed using a radioactive seed or a wire, as illustrated in Figures 4a–d. A bracketed seed or wire may also be placed under MRI guidance to localize a large area of enhancement which may not have a mammographic or sonographic correlate, as illustrated in Figures 5a–f and 6a–d, respectively.[1012]
Caveat for all magnetic resonance imaging-guided seed localization procedures
The preparation for MRI-guided I-125 seed localization must take into consideration the rare possibility of dropping a seed in MRI Zone 3 or Zone 4 where current Geiger counters are inadmissible.[13] Until MRI-safe Geiger counters are available, prevention of dropping the seed is of utmost importance. When such a procedure is necessary, we employ a minimum of four people who are assigned the sole task of verifying visual confirmation of where the seed is at any time. From the time, the seed is handled from Zone 3 to Zone 4; the radiologist announces where the seed is and waits for verification by all the assigned observers. Before the procedure, the procedural area including a larger work area is draped, paying close attention to cover any small gaps between equipment interfaces. Whenever possible, white draping is selected.
Digital tomosynthesis
Tomosynthesis-guided procedures can be approached in much the same way as CT-guided procedures. As such, the direction of approach can be orthogonal (through an opening in the compression plate), in-plane (free handed between the detector and the compression plate, or with a lateral arm), or oblique (free handed usually between the detector and the compression plate). We show a digital tomosynthesis approach to localize a sonographically occult positive axillary LN in Figures 7a–e and 8a–c. Because the seed is often placed in the same direction as the direction of compression, we have found that there is a tendency for the seed to sometimes migrate when compression is released. To lessen this “accordion effect,” we occasionally release some compression (~5–10 Newtons) just before seed placement to determine if the seed should be deployed. Alternatively, we sometimes place the seed needle perpendicular to the direction of compression, or if placed in the direction of compression, we acquire another view in-plane with the needle (just as in a digital non-tomosynthesis technique) before deployment of the seed.
Ultrasound localization using iodinated contrast
In cases where a possible clipped metastatic LN is identified on ultrasound, but is not definitive, either because the LN has decreased in size post-NAT or due to nonvisualization of clip, a small amount (approximately 1–1.5 cc) of 1:10 dilution iodinated contrast (e.g., Omnipaque 350) may be injected into the suspected LN using sonographic guidance, and a mediolateral (ML) or ML oblique view mammogram may be obtained. This will confirm if the suspected LN identified on ultrasound is indeed the clipped node as it will contain radiopaque contrast material. The patient can then be returned to ultrasound, and the node may be localized with sonographic guidance. This technique is illustrated in Figures 9a–g.
CONCLUSION
When the identified specific lesion cannot be localized in the breast or axilla using conventional methods, other techniques may be employed to aid the surgeon in identifying the site of malignancy.[114151617181920] At our medical facility, we have had success in localizing the more challenging cases using these techniques. Although it sometimes requires logistical and scheduling coordination with other divisions such as CT intervention, we have so far not had a case we were unable to perform preoperative localization.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Available FREE in open access from: http://www.clinicalimagingscience.org/text.asp?2018/8/1/54/247345
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