Intraoperative sentinel lymph node evaluation: Optimizing surgical pathology practices in an era of changing clinical management

Update on Sentinel Lymph Node Methods and Pathology in Breast Cancer

Breast cancer stands out as the most commonly diagnosed cancer among women globally. Precise lymph node staging holds critical significance for both predicting outcomes in early-stage disease and formulating effective treatment strategies to control regional disease progression in breast cancer patients. No imaging technique possesses sufficient accuracy to identify lymph node metastases in the early stages (I or II) of primary breast cancer. However, the sentinel node procedure emerges as a valuable approach for identifying metastatic axillary nodes. The sentinel lymph node is the hypothetical first lymph node or group of nodes draining a cancer. In case of established cancerous dissemination, it is postulated that the sentinel lymph nodes are the target organs primarily reached by metastasizing cancer cells from the tumor. The utilization of the sentinel node technique has brought about changes in the assessment of lymph nodes. It involves evaluating the sentinel node during surgery, enabling prompt lymph node dissection when the sentinel node procedure is positive. Additionally, histological ultra-stratification is employed to uncover occult metastases. This review aims to provide an update of this valuable technique, with focus on the practical aspects of the procedure and the different histological protocols of sentinel node evaluation in breast cancer.

A prospective comparison of a modified miniaturised hand-held epifluorescence microscope and touch imprint cytology for evaluation of axillary sentinel lymph nodes intraoperatively in breast cancer patients

BACKGROUND

The management of axillary lymph nodes in early-stage breast cancer patients has changed considerably, with the primary focus shifting from the examination of sentinel lymph nodes (SLNs) to toward the detection of all macro-metastases. However, current methods, such as touch imprint cytology (TIC) and frozen sections, are inadequate for clinical needs. To address this issue, we proposed a novel miniaturised epifluorescence widefield microscope (MEW-M) to assess SLN status intraoperatively for improved diagnostic efficiency.

METHODS

A prospective, side-by-side comparison of intraoperative SLN evaluation between MEW-M and TIC was performed.

RESULTS

A total of 73 patients with 319 SLNs consecutive enrolled in this study. MEW-M showed significantly superior image quality compared to TIC (median score 3.1 vs 2.1, p < 0.0001) and had a shorter time to issue results (10.3 vs 19.4 min, p < 0.0001). Likelihood ratio analysis illustrated that the positive likelihood ratio value of MEW-M compared with TIC was infinitely great vs 52.37 (95% CI, 21.96-124.90) in model 1 (classifying results into negative/positive), infinitely great vs 52.37 (95% CI, 21.96-124.90) in model 2 (classifying results into macro-metastasis/others, and TIC results followed the same classification as model 1), respectively. Similarly, the negative likelihood ratio values of MEW-M compared with TIC were 0.055 (95% CI, 0.018-0.160) and 0.074 (95% CI, 0.029-0.190) in model 1; and 0.019 (95% CI, 0.003-0.130) vs 0.020 (95% CI, 0.003-0.140) in model 2, respectively.

CONCLUSIONS

MEW-M is a promising technique that can be utilised to provide a rapid and accurate intraoperative assessment of SLN in a clinical setting to help improve decision-making in axillary surgery.

Prospective Comparison of Intraoperative Touch Imprint Cytology and Frozen Section Histology on Axillary Sentinel Lymph Nodes in Early Breast Cancer Patients

INTRODUCTION

Since the late 1970s, sentinel lymph node biopsy (SLNB) has been used for several solid malignancies to identify lymph node metastases. This procedure is associated with less surgical morbidity than complete lymphadenectomy. Recent evidence suggests that axillary lymphadenectomy is not required for breast sentinel nodes with micrometastases (≤2 mm). Current clinical management of sentinel nodes indicates that only macrometastases (>2 mm) should be detected intraoperatively. In Japan, an intraoperative histopathological frozen section (FS) method is used to identify lymph node metastases, but this method takes more than 30 min and requires complex techniques and expensive equipment. Touch imprint cytology (TIC) is an easier, less expensive, and faster method, but its sensitivity has been shown to be low.

OBJECTIVE

The purpose of this study was to determine if TIC is more useful than FS in identifying macrometastases in sentinel lymph nodes in preoperative node-negative breast cancer operations.

METHODS

A prospective review of 49 consecutive patients with node-negative breast cancer treated with SLNB and intraoperative TIC and FS between November 2017 and June 2019 was performed. TIC samples were stained using Papanicolaou and Diff-Quick stains. Results were compared with routine postoperative paraffin sections.

RESULTS

With TIC, the Papanicolaou stain took a mean of 12 min, and the Diff-Quick stain took a mean of 10 min. Results of both TIC stain methods were the same. In contrast, the FS method took a mean of 80 min (including the transfer of specimens to a different hospital with the necessary equipment). TIC confirmed macrometastases in 5 cases. All macrometastases were diagnosed equally by the 2 techniques. Both the sensitivity and specificity of TIC were 100% for detection of macrometastases.

CONCLUSION

TIC of SLNB for breast cancer is an easy and useful method for the detection of macrometastases of breast sentinel nodes.

[Pathological process for sentinel lymph node]

Sentinel node is defined as the first node to receive drainage from a primary tumor and seems to reflect the nodal status in the lymphatic drainage of the tumor. Sentinel node technique has modified the pathological examination of lymph nodes, with intraoperative evaluation of sentinel node, allowing immediate lymph node dissection in case of positive sentinel node, and histological ultrastratification to detect occult metastases. This is a literature review of different histological protocols of sentinel node according to different organs. Except for sentinel node in breast cancer and melanoma, intraoperative examination of sentinel node is helpful using frozen section, more sensitive than touch imprint cytology. Sentinel node should be embedded in paraffin block entirely after gross sectioning at two millimeters intervals parallel to the long axis of the node. Histological ultrastaging with serial sections can be helpful, but the number of sections and the interval between them is not codified. Three sections at 200-250 microns can identify the majority of micrometastases (<2mm and >200 microns). Systematic immunohistochemistry of sentinel node is not necessary for breast cancers, since isolated tumor cells do not modify the therapeutic strategy, but remains useful in other organs.