Localization of nonpalpable breast lesions

Innovations in the localization techniques for non-palpable breast lesions: Make invisible visible

Non-palpable breast cancer lesions pose a challenge for surgeons to resect cancer lesions. Making 'invisible' lesions 'visible' is the main strategy. Currently, multiple preoperative localization techniques have been applied in clinical. Among them, wire-guided localization (WGL) is the most common procedure due to its convenience and low cost. However, its limitations including discomfort, wire migration and the coupling of localization and operation procedures cause troubles for surgeons and patients. The desire for localization methods improvement, accompanied by the advance of emerging science and technology, leads to the development of a series of locating approaches for breast non-palpable lesions, aiming to improve locating accuracy while reducing adverse events. These emerging methods have undergone improvements from steel wire to functional particles, from radioactivity to non-radioactive, which help doctors and patients choose a more appropriate scheme. This review outlines the principles, procedures, advantages and disadvantages of these locating methods, and highlights the latest progress and related clinical data on innovative locating approaches. Finally, we briefly discuss the current challenges and future opportunities for the clinical application of these localization approaches.

Efficacy of indocyanine green fluorescence for the identification of non-palpable breast tumours: systematic review

BACKGROUND

Accurate tumour localization is crucial for precise surgical targeting and complete tumour removal. Indocyanine green fluorescence, an increasingly used technique in oncological surgery, has shown promise in localizing non-palpable breast tumours. The aim of this systematic review was to describe the efficacy of indocyanine green fluorescence for the identification of non-palpable breast tumours.

METHODS

A systematic literature search was performed in PubMed, Embase, and the Cochrane Library, including studies from 2012 to 2023. Studies reporting the proportion of breast tumours identified using indocyanine green fluorescence were included. The quality of the studies and their risk of bias were appraised using the Methodological Index for Non-Randomized Studies ('MINORS') tool. The following outcomes were collected: identification rate, clear resection margins, specimen volume, operative time, re-operation rate, adverse events, and complications.

RESULTS

In total, 2061 articles were screened for eligibility, resulting in 11 studies, with 366 patients included: two RCTs, three non-randomized comparative studies, four single-arm studies, and two case reports. All studies achieved a 100 per cent tumour identification rate with indocyanine green fluorescence, except for one study, with an identification rate of 87 per cent (13/15). Clear resection margins were found in 88-100 per cent of all patients. Reoperation rates ranged from 0.0 to 5.4 per cent and no complications or adverse events related to indocyanine green occurred.

CONCLUSION

Indocyanine green fluorescence has substantial theoretical advantages compared with current routine localization methods. Although a limited number of studies were available, the current literature suggests that indocyanine green fluorescence is a useful, accurate, and safe technique for the intraoperative localization of non-palpable breast tumours, with equivalent efficacy compared with other localization techniques, potentially reducing tumour-positive margins.

Biopsy marker localization with thermo-acoustic ultrasound for lumpectomy guidance

PURPOSE

Almost one in four lumpectomies fails to fully remove cancerous tissue from the breast, requiring reoperation. This high failure rate suggests that existing lumpectomy guidance methods are inadequate for allowing surgeons to consistently identify the proper volume of tissue for excision. Current guidance techniques either provide little information about the tumor position or require surgeons to frequently switch between making incisions and manually probing for a marker placed at the lesion site. This article explores the feasibility of thermo-acoustic ultrasound (TAUS) to enable hands-free localization of metallic biopsy markers throughout surgery, which would allow for continuous visualization of the lesion site in the breast without the interruption of surgery. In a TAUS-based localization system, microwave excitations would be transmitted into the breast, and the amplification in microwave absorption around the metallic markers would generate acoustic signals from the marker sites through the thermo-acoustic effect. Detection and ranging of these signals by multiple acoustic receivers on the breast could then enable marker localization through acoustic multilateration.

METHODS

Physics simulations were used to characterize the TAUS signals generated from different markers by microwave excitations. First, electromagnetic simulations determined the spatial pattern of the amplification in microwave absorption around the markers. Then, acoustic simulations characterized the acoustic fields generated from these markers at various acoustic frequencies. TAUS-based one-dimensional (1D) ranging of two metallic markers-including a biopsy marker that is FDA-approved for clinical use-immersed in saline was also performed using a bench-top setup. To perform TAUS acquisitions, a microwave applicator was driven by 2.66 GHz microwave signals that were amplitude-modulated by chirps at the desired acoustic excitation frequencies, and the resulting TAUS signal from the markers was detected by an ultrasonic transducer.

RESULTS

The simulation results show that the geometry of the marker strongly impacts the quantity and spatial pattern of both the microwave absorption around the marker and the resulting TAUS signal generated from the marker. The simulated TAUS signal maps and acoustic frequency responses also make clear that the marker geometry plays an important role in determining the overall system response. Using the bench-top setup, TAUS detection and 1D localization of the markers were successfully demonstrated for multiple different combinations of microwave applicator and metallic marker. These initial results indicate that TAUS-based localization of biopsy markers is feasible.

CONCLUSIONS

Through microwave excitations and acoustic detection, TAUS can be used to localize metallic biopsy markers. With further development, TAUS opens new avenues to enable a more intuitive lumpectomy guidance system that could help to achieve better lumpectomy outcomes.

Optimization of Wire-guided Technique With Bracketing Reduces Resection Volumes in Breast-conserving Surgery for Early Breast Cancer

BACKGROUND

Wire-guided localization (WGL) of early breast cancer can be facilitated using multiple wires, which is called bracketing wire-guided localization (BWL). The primary aim of this study is to compare BWL and conventional WGL regarding minimization of resection volumes without compromising margin status. Secondly, BWL is evaluated as an alternative method for intraoperative ultrasound (US) guidance in poorly definable breast tumors on US.

PATIENTS AND METHODS

In this retrospective cohort study, patients with preoperatively diagnosed breast cancer undergoing wide local excision between January 2016 and December 2018 were analyzed. Patients with multifocal disease or neoadjuvant treatment were excluded from this study. Optimal resection with minimal healthy breast tissue removal was assessed using the calculated resection ratio (CRR).

RESULTS

BWL was performed in 17 (9%) patients, WGL in 44 (22%), and US in 139 (70%). The rate of negative margins was comparable in all 3 groups. The CRR was significantly smaller for BWL (0.6) than WGL (1.3) in tumors larger than 1.5 cm. Additionally, BWL (0.8) led to smaller CRRs than US (1.7). This could be explained by the high number of small tumors (≤ 1.5 cm) in the US group for which greater CRRs are obtained than for large tumors (> 1.5 cm) (1.9 vs. 1.4; P = .005).

CONCLUSION

For breast tumors larger than 1.5 cm, BWL achieves more optimal resection volumes without compromising margin status compared with WGL. Moreover, BWL seems a suitable alternative to US in patients with poorly ultrasound-visible breast tumors and patients with a small tumor in a (large) breast.

Precision biopsy of breast microcalcifications: An improvement in surgical excision

The aim of the present study was to improve the conventional wire-guided localization biopsy (WGLB) of breast microcalcifications to overcome disadvantages associated with the procedure, including inaccurate localization and large specimen volume. The novel approach described in the present study was termed double wire-guided localization and rotary cutting biopsy (DWGLB). Prior to surgery, the precise localization of the lesions was assessed using two wires under the assistance of mammography X-ray and ultrasound, followed by complete excision of the lesions using a novel rotary cutting tool. The cylindrical specimen was placed on a scaled specimen holder for pathological examination. DWGLB was performed in 108 patients with the classification of as Breast Imaging Reporting and Data System score 4A. Percutaneous localization of the lesions guided by a mammography X-ray and ultrasound were successful in all 108 lesions (100%) with one puncture attempt. The lesions were precisely excised in all of 108 patients, and included 13 malignant lesions (DCIS of breast in 7 cases, DCIS with focal invasive carcinoma in 3 cases and invasive ductal carcinoma in 3 cases). The average distance of the BARD Dualok to the lesion was 4.1 mm; the average weight of specimens was 8.5 g. Compared with WGLB, DWGLB offers several advantages, including more accurate localization of lesions, a more standardized biopsy method and a smaller specimen volume. DWGLB can also provide the precise position of lesions in the specimen for further pathological examination.

Injectable iodine-125 labeled tissue marker for radioactive localization of non-palpable breast lesions

We have developed a ¹²⁵I-radiolabeled injectable fiducial tissue marker with the potential to replace current methods used for surgical guidance of non-palpable breast tumors. Methods in routine clinical use today such as radioactive seed localization, radio-guided occult lesion localization and wire-guided localization suffers from limitations that this injectable fiducial tissue marker offers solutions to. The developed ¹²⁵I-radiolabeled injectable fiducial tissue marker is based on highly viscous sucrose acetate isobutyrate. The marker was readily inserted in NMRI mice and proved to be spatially well-defined and stable over a seven day period with excellent CT contrast (>1500 HU), enabling fluoroscopic visualization of the marker during placement. The radioactivity remains strongly associated with the marker during the implantation period, which limits exposure to healthy tissue. Biodistribution studies show that there is negligible radioactivity in all non-tumor tissues sampled, with the exception of the thyroid gland, where limited accumulation was observed (0.06% of injected dose after 7 days). Based on the excellent performance of the marker and the fact that it can be delivered through thin hypodermic needles (≥27G), the marker holds great promise for clinical application, since patient discomfort is reduced significantly compared to current methods.

STATEMENT OF SIGNIFICANCE

A new type of tissue marker for local administration to non-palpable breast tumors has been developed. The surgical guidance marker is based on derivatives of the biomaterial sucrose acetate isobutyrate and unlike currently used markers it is injectable in the tissue using thin needles, reducing the discomfort to the patients significantly. The marker confers CT contrast and has radioactive properties, meaning it also could find use in brachytherapy. The design of the iodine-125 labeled fiducial tissue marker enables control of dosimetry as well as a choice of iodine isotope used. The marker is anticipated to be clinical applicable due to its contrast performance in mice and its potential for enhanced flexibility in surgical procedures, compared to current methods.

A fiber optoacoustic guide with augmented reality for precision breast-conserving surgery

Lumpectomy, also called breast-conserving surgery, has become the standard surgical treatment for early-stage breast cancer. However, accurately locating the tumor during a lumpectomy, especially when the lesion is small and nonpalpable, is a challenge. Such difficulty can lead to either incomplete tumor removal or prolonged surgical time, which result in high re-operation rates (~25%) and increased surgical costs. Here, we report a fiber optoacoustic guide (FOG) with augmented reality (AR) for sub-millimeter tumor localization and intuitive surgical guidance with minimal interference. The FOG is preoperatively implanted in the tumor. Under external pulsed light excitation, the FOG omnidirectionally broadcasts acoustic waves through the optoacoustic effect by a specially designed nano-composite layer at its tip. By capturing the acoustic wave, three ultrasound sensors on the breast skin triangulate the FOG tip's position with 0.25-mm accuracy. An AR system with a tablet measures the coordinates of the ultrasound sensors and transforms the FOG tip's position into visual feedback with <1-mm accuracy, thus aiding surgeons in directly visualizing the tumor location and performing fast and accurate tumor removal. We further show the use of a head-mounted display to visualize the same information in the surgeons' first-person view and achieve hands-free guidance. Towards clinical application, a surgeon successfully deployed the FOG to excise a "pseudo tumor" in a female human cadaver. With the high-accuracy tumor localization by FOG and the intuitive surgical guidance by AR, the surgeon performed accurate and fast tumor removal, which will significantly reduce re-operation rates and shorten the surgery time.

Predictors of re-excision in wire-guided wide local excision for early breast cancer: a Western Australian multi-centre experience

BACKGROUND

A significant proportion of breast cancers present as impalpable lesions requiring radiological guidance prior to surgical excision, commonly by hook-wire placement. Complete lesion excision is an essential part of treatment, and re-excision may be needed to ensure this and minimize local recurrence. We explore a 1-year audit of re-excision of hook-wire-guided excisions in two large public breast units in Western Australia and define factors associated with the requirement for re-excision.

METHODS

A retrospective review of wire-localized wide local excisions for early breast cancer in 2009 at two tertiary breast centres in Western Australia.

RESULTS

Of 148 localized lesions, 44 (30%) underwent re-excision. The only significant preoperative finding was the location of tumour in the breast. The intra-operative specimen radiograph provided useful information that influenced re-excision. Smaller (≤5 mm) and larger (>20 mm) tumours on final pathological size were more likely to undergo re-excision as well as a larger difference in actual size to predicted size. The presence of ductal carcinoma in situ (DCIS) increased re-operation, as did multifocality.

CONCLUSION

This study highlights factors that should make the surgeon more cautious for re-excision. Suspicion of DCIS, especially at the periphery of tumours, and a central tumour location increase risk. Lesion localization techniques play an important role in minimizing risk while maintaining cosmesis.

The use of radioactive iodine-125 seed localization in patients with non-palpable breast cancer: a comparison with the radioguided occult lesion localization with 99m technetium

BACKGROUND

Radioactive Seed Localization with a radioactive iodine-125 seed (RSL) and Radioguided Occult Lesion Localization with 99mTechnetium colloid (ROLL) are both attractive alternatives to wire localization for guiding breast conserving surgery (BCS) of non-palpable breast cancer. The aim of this study was to evaluate and compare the efficacy of RSL and ROLL.

METHODS

We retrospectively analyzed 387 patients with unifocal non-palpable ductal carcinoma in situ (DCIS) or invasive carcinoma treated with BCS at the Netherlands Cancer Institute. In total 403 non-palpable lesions were localized either by RSL (N = 128) or by ROLL (N = 275). Primary outcome measures were positive margins and re-excision rates; the secondary outcome measure was weight of the specimen.

RESULTS

Pre-operative mammography or ultrasound showed similar sizes of DCIS and invasive tumours in both RSL and ROLL groups. In the RSL group, more lesions were DCIS (58%) than in the ROLL group, where 32% of the lesions were pure DCIS. The proportions of focally positive margins (11% vs. 10%) and more than focally positive margins (9% vs. 9%) were comparable between the RSL and the ROLL group, resulting in the same re-excision rate in both RSL and ROLL groups (9% vs. 10%). For DCIS lesions, the specimen weight was significantly lower in the RSL group than in the ROLL group after adjusting for tumour size on mammography (12 g; 95% CI 2.6-21).

CONCLUSION

Margin status and re-excision rates were comparable for RSL and ROLL in patients with non-palpable breast lesions. Because of the significant lower weight of the resected specimen in DCIS, the feasibility of position verification of the I-125 seed and more convenient logistics, we favour RSL over ROLL to guide breast-conserving therapy.

Heading toward radioactive seed localization in non-palpable breast cancer surgery? A meta-analysis

Wire-guided localization is the most commonly used technique for intraoperative localization of non-palpable breast cancer. Radioactive seed localization (RSL) is becoming more popular and seems to be a reliable alternative for intraoperative lesion localization. The purpose of the present meta-analysis was to evaluate the use of RSL. Primary study outcomes were irradicality and re-excision rates. In total 3168 patients were included. The clinical adaptation shows growing confidence in RSL and further growth is expected.

Feasibility of preoperative (125)I seed-guided tumoural tracer injection using freehand SPECT for sentinel lymph node mapping in non-palpable breast cancer

Background

This study was designed to explore the feasibility of replacing the conventional peri-/intratumoural ultrasound (US)-guided technetium-99m albumin nanocolloid (^99mTc-nanocolloid) administration by an injection of the same tracer guided by a freehand single-photon emission computed tomography (SPECT) device in patients with non-palpable breast cancer with an iodine-125 (¹²⁵I) seed as tumour marker, who are scheduled for a sentinel lymph node biopsy (SLNB). This approach aimed to decrease the workload of the radiology department, avoiding a second US-guided procedure.

Methods

In ten patients, the implanted ¹²⁵I seed was primarily localised using freehand SPECT and subsequently verified by conventional US in order to inject the ^99mTc-nanocolloid. The following 34 patients were injected using only freehand SPECT localisation. In these patients, additional SPECT/CT was acquired to measure the distance between the ^99mTc-nanocolloid injection depot and the ¹²⁵I seed. In retrospect, a group of 21 patients with US-guided ^99mTc-nanocolloid administrations was included as a control group.

Results

The depth difference measured by US and freehand SPECT in ten patients was 1.6 ± 1.6 mm. In the following 36 ¹²⁵I seeds (34 patients), the average difference between the ¹²⁵I seed and the centre of the ^99mTc-nanocolloid injection depot was 10.9 ± 6.8 mm. In the retrospective study, the average distance between the ¹²⁵I seed and the centre of the ^99mTc-nanocolloid injection depot as measured in SPECT/CT was 9.7 ± 6.5 mm and was not significantly different compared to the freehand SPECT-guided group (two-sample Student's t test, p = 0.52).

Conclusion

We conclude that using freehand SPECT for ^99mTc-nanocolloid administration in patients with non-palpable breast cancer with previously implanted ¹²⁵I seed is feasible. This technique may improve daily clinical logistics, reducing the workload of the radiology department.

Intraoperative ultrasound guidance is associated with clear lumpectomy margins for breast cancer: a systematic review and meta-analysis

PURPOSE

Margin status is one of the most important predictors of local recurrence after breast conserving surgery (BCS). Intraoperative ultrasound guidance (IOUS) has the potential to improve surgical accuracy for breast cancer. The purpose of the present meta-analysis was to determine the efficacy of IOUS in breast cancer surgery and to compare the margin status to that of the more traditional Guide wire localization (GWL) or palpation-guidance.

METHODS

We searched the database of PubMed for prospective and retrospective studies about the impact of IOUS on margin status of breast cancer, and a meta-analysis was conducted.

RESULTS

Of the 13 studies included, 8 were eligible for the impact of IOUS on margin status of non-palpable breast cancers, 4 were eligible for palpable breast cancers, and 1 was for both non-palpable and palpable breast cancers. The rate of negative margins of breast cancers in IOUS group was significantly higher than that in control group without IOUS (risk ratio (RR)  = 1.37, 95% confidence interval (CI)  = 1.18-1.59 from 7 prospective studies, odds ratio (OR)  = 2.75, 95% CI  = 1.66-4.55 from 4 retrospective studies). For non-palpable breast cancers, IOUS-guidance enabled a significantly higher rate of negative margins than that of GWL-guidance (RR  = 1.26, 95% CI  = 1.09-1.46 from 6 prospective studies; OR  = 1.45, 95% CI  = 0.86-2.43 from 2 retrospective studies). For palpable breast cancers, relative to control group without IOUS, the RR for IOUS associated negative margins was 2.36 (95% CI  = 1.26-4.43) from 2 prospective studies, the OR was 2.71 (95% CI  = 1.25-5.87) from 2 retrospective studies.

CONCLUSION

This study strongly suggests that IOUS is an accurate method for localization of non-palpable and palpable breast cancers. It is an efficient method of obtaining high proportion of negative margins and optimum resection volumes in patients undergoing BCS.

Radioactive seed localization for non-palpable breast cancer

BACKGROUND

Radioactive seed localization (RSL) is an alternative to wire localization for guiding surgical excision of non-palpable breast cancer. This review provides an overview of the available evidence on the accuracy of RSL in patients undergoing breast-conserving surgery.

METHODS

PubMed, Embase and the Cochrane Library were searched systematically in January 2012 for studies that addressed localization of non-palpable breast cancer using an iodine-125-labelled seed. Studies were deemed eligible if they reported on the proportion of patients with tumour-positive margins after RSL, the proportion of patients needing re-excision after RSL, and procedural complications.

RESULTS

Six studies reported data on RSL in 1611 patients with non-palpable breast lesions. Overall complete resection rates ranged from 73 to 96.7 per cent. Three studies included over 300 patients, and complete resection rates in these studies varied between 89.5 and 96.7 per cent. The risk of seed migration and failure of seed placement ranged from 0 to 0.6 per cent and 0 to 7.2 per cent respectively.

CONCLUSION

Available scientific evidence suggests that RSL is a safe and accurate technique for localization of non-palpable breast lesions.

Cost-effectiveness of radioguided occult lesion localization (ROLL) versus wire-guided localization (WGL) in breast conserving surgery for nonpalpable breast cancer: results from a randomized controlled multicenter trial

BACKGROUND

Accurate preoperative localization of nonpalpable breast cancer is essential to achieve complete resection. Radioguided occult lesion localization (ROLL) has been introduced as an alternative for wire-guided localization (WGL). Although efficacy of ROLL has been established in a randomized controlled trial, cost-effectiveness of ROLL compared with WGL is not yet known. The objective of this study was to determine whether ROLL has acceptable cost-effectiveness compared with WGL.

METHODS

An economic evaluation was performed along with a randomized controlled trial (ClinicalTrials.gov, No. NCT00539474). Women (>18 years) with histologically proven nonpalpable breast cancer and eligible for breast conserving treatment with sentinel node procedure were randomized to ROLL (n = 162) or WGL (n = 152). Empirical data on direct medical costs were collected, and changes in quality of life were measured over a 6-month period. Bootstrapping was used to assess uncertainty in cost-effectiveness estimates, and sensitivity of the results to the missing data approach was investigated.

RESULTS

In total, 314 patients with 316 invasive breast cancers were enrolled. On average ROLL required the same time as WGL for the surgical procedure (119 vs 118 min), resulted in a 7 % higher reinterventions risk, and 13 % more complications. Quality of life effects were similar (difference 0.00 QALYs 95 % CI (-0.04-0.05). Total costs were also similar for ROLL and WGL (+<euro>26 per patient 95 % CI <euro>-250-311).

CONCLUSION

ROLL is comparable to WGL with respect to both costs and quality of life effects as measured with the EQ5D and will therefore not lead to more cost-effective medical care.

Efficacy of 'radioguided occult lesion localisation' (ROLL) versus 'wire-guided localisation' (WGL) in breast conserving surgery for non-palpable breast cancer: a randomised controlled multicentre trial

For the management of non-palpable breast cancer, accurate pre-operative localisation is essential to achieve complete resection with optimal cosmetic results. Radioguided occult lesions localisation (ROLL) uses the radiotracer, injected intra-tumourally for sentinel lymph node identification to guide surgical excision of the primary tumour. In a multicentre randomised controlled trial, we determined if ROLL is superior to the standard of care (i.e. wire-guided localisation, WGL) for preoperative tumour localisation. Women (>18 years.) with histologically proven non-palpable breast cancer and eligible for breast conserving treatment with sentinel node procedure were randomised to ROLL or WGL. Patients allocated to ROLL received an intra-tumoural dose of 120 Mbq technetium-99 m nanocolloid. The tumour was surgically removed, guided by gamma probe detection. In the WGL group, ultrasound- or mammography-guided insertion of a hooked wire provided surgical guidance for excision of the primary tumour. Primary outcome measures were the proportion of complete tumour excisions (i.e. with negative margins), the proportion of patients requiring re-excision and the volume of tissue removed. Data were analysed according to intention-to-treat principle. This study is registered at ClinincalTrials.gov, number NCT00539474. In total, 314 patients with 316 invasive breast cancers were enrolled. Complete tumour removal with negative margins was achieved in 140/162 (86 %) patients in the ROLL group versus 134/152 (88 %) patients in the WGL group (P = 0.644). Re-excision was required in 19/162 (12 %) patients in the ROLL group versus 15/152 (10 %) (P = 0.587) in the WGL group. Specimen volumes in the ROLL arm were significantly larger than those in the WGL arm (71 vs. 64 cm(3), P = 0.017). No significant differences were seen in the duration and difficulty of the radiological and surgical procedures, the success rate of the sentinel node procedure, and cosmetic outcomes. In this first multicentre randomised controlled comparison of ROLL versus WGL in patients with histologically proven breast cancer, ROLL is comparable to WGL in terms of complete tumour excision and re-excision rates. ROLL, however, leads to excision of larger tissue volumes. Therefore, ROLL cannot replace WGL as the standard of care.

Intraoperative ultrasound guidance for excision of non-palpable invasive breast cancer: a hospital-based series and an overview of the literature

Intraoperative ultrasound (IOUS) can be used in the operation theatre for localization of non-palpable breast cancers. In this prospective cohort study, we compared the yield of IOUS to guidewire localization (GWL). A total of 258 consecutive patients with non-palpable invasive breast cancer underwent breast conserving surgery between 1999 and 2010. GWL was performed in 138 (54 %) and IOUS in 120 (46 %) patients. Tumor dimensions, resection volume, margin status and re-excision rates were compared by means of multivariate regression analysis. The groups were similar in terms of age, histological subtype and presence of DCIS. Lesions in the IOUS group were larger (1.24 vs. 0.98 cm, P < 0.001), while microcalcifications were more common in the GWL group (19 vs. 3 %, P < 0.001). Even after stratification for tumor diameter, presence of DCIS and findings on mammography, resection volumes were similar in both groups. Tumor-free resection margins were obtained in >93 % of patients (93.5 % with GWL vs. 93.3 % with IOUS, P = 0.958) and re-excision was performed in 11 % of patients undergoing GWL and 12.5 % of patients undergoing IOUS (P = 0.684). For localization of non-palpable breast cancer, IOUS is a reliable alternative to GWL, as it achieves similar results in terms of complete tumor removal, re-excision rate and excised volume.