Giuliano et al. [8] are the first surgeons to introduce the technique of SLN for the assessment of nodal status in early node-negative breast cancer, and the technique has become a standard procedure for breast cancer patients. SLN biopsy had less morbidity compared with ALND and the success of the procedure depends on co-operation between the multidisciplinary team of specialist surgeons, pathologists, and nuclear medicine. As with any technique, the frozen section has its limitation such as cost, labor, a requirement of a skilled histopathology technician, and dedicated histopathologists [9].
So this study is performed to evaluate the performance of intraoperative US as a replacement tool for the frozen section in the ex vivo evaluation of axillary lymph node status in patients with early breast cancer in countries with limited resources and difficulties in establishing intraoperative frozen section for breast cancer patients.
Ultrasound examination of axillary LN has its characteristic features for suggesting malignant lymph node involvement and has been established as a pre-operative non-invasive tool to determine axillary LN status [10].
Further management of SLNB positive nodes was guided by ACOSOG Z0011 criteria for the management of SLNB in T1-2 N0 patients according to NCCN guidelines [11].
In the current study, SLNB was done using 1% MB with a 100% identification rate (IR). It was found that identification rates for SLNB have increased over time from 88% in 1992–2000 to 97% in 2007–2012, the increase in IR during the last 18 years is likely due to the increase in gained experience by the surgeons performing SLNB [12].
In the ACOSOG Z0010 trial, the percent of failed SNB with blue dye was 1.4%, radiocolloid 2.3%, and the combination 1.2%, so some authors claim that the addition of radiocolloids to blue dye in SLNB does not increase the identification rate to the degree that justifies its costs and restrictions in its use [13].
The commonly used technique for intraoperative detection of sentinel lymph node metastasis is a frozen section examination; its reported sensitivity range from 19 to 75% [14]. However, with increased experience, Wong et al. [15] reported the overall false-negative rate for the frozen section in SLN was 13.5%. The authors considered this rate is acceptable.
In the current study, all lymph node specimens were examined by a dedicated pathologist; it was found that the sensitivity, specificity, PPV, NPV, and accuracy of frozen examination in the detection of positive lymph nodes were 90.91%, 96%, 90.91%, 96%, and 94.44%, respectively.
This study has shown significantly improved results which may be due to serial slicing of lymph nodes, examining multiple levels, and the proven expertise of the histopathologist.
In the current study, all lymph node specimens were examined by a dedicated pathologist; it was found that the sensitivity, specificity, PPV, NPV, and accuracy of frozen examination in the detection of positive lymph nodes were 90.91%, 96%, 90.91%, 96%, and 94.44%, respectively. This study has shown significantly improved results which may be due to serial slicing of lymph nodes, examining multiple levels, and the proven expertise of the histopathologist.
Our results were in agreement with Krag et al. [16], who reported 90.2% sensitivity of sentinel lymph node examination in breast cancer patients 9.8% false-negative results.
Also, Marano et al. [17] have retrospectively evaluated 359 sentinel node biopsies in breast cancer from January 2011 to December 2018, performing an intraoperative examination. It results in 12.8% “false negative” rate, in which only 4.2% in macrometastases, with an overall sensitivity of 68.4% (macrometastases, 86%; micrometastases, 11%), an overall specificity of 98.7% and an overall accuracy of 89.7%.
In this study, we explored the role of another new technique by using intraoperative ultrasound for the evaluation of the ex vivo SLN before being examined by the frozen section during the operation and finally by the paraffin section postoperatively. It is a possible future technique where intraoperative ultrasound assessment of the ex vivo SLN detects the abnormal nodal architecture (cortical thickening > 3 ml, loss of the normal hyperechoic hilum). Cortical thickening is an early finding, with eccentric thickening having a higher predictive value for node involvement than diffuse thickening. A cutoff value of 3 mm for defining a thickened versus normal cortex is most common, but not universally, used. The presence of a tumor within the node may lead to the effacement of the fatty hilum and alteration in nodal contours [18].
Suspicious criteria for axillary LN in US evaluation include increase spherical index, nodal hypoechogenicity, and cortical thickness. Along with asymmetrical cortical thickening, an abnormal lymph node can be defined. Cortical thickness of ≥ 3 mm showed 96% sensitivity and 87% specificity in the detection of malignant nodes; other trials with a larger sample size used values ranging between 2.3 and 4 mm [18].
We categorized the retrieved lymph node as being suspicious depending on the measurement of its cortical thickness and whether it has a uniform or non-uniform cortical thickness (Figs. 1 and 2). Both used criteria showed a statically significant correlation with final histopathological results (p-value < 0.001) with a cutoff value for cortical thickness = 2.65 mm.
The sensitivity, specificity, PPV, NPV, and accuracy of ultrasound in the detection of positive lymph nodes were 95.45%, 82%, 70%, 97.62%, and 86.11%, respectively.
By comparing ultrasonographic assessment of ex vivo lymph nodes with frozen section examination to paraffin section examination of the lymph nodes, we found that frozen section examination is superior to the ultrasonographic assessment of ex vivo lymph in detecting positive cases when compared to paraffin section examination (Figs. 3 and 4).
In the current study, injection of 1% MB was safe and no allergic or anaphylactic reactions were observed during the SLNB procedure, following most published studies, except Teknos et al. [19] who reported a case of pulmonary edema during an SLN procedure using MB.
Follow-up of the patients with positive SLNB for an average of 1 year showed no locoregional recurrence in any of the patients in the study group.
Study limitation
This study described the results of a single-center with a small number of studied populations.