**2.8 Paramagnetic tracer**

New tracers are being applied. Recently, the Central-European SentiMAG multicentre clinical trial compared the use of the standard tracer (99mTcnanocolloid and MB) with superparamagnetic iron oxide (SPIO) labelled nanoparticles, marketed under the name Sienna<sup>+</sup> ®. The preliminary results indicated comparable detection rates of 97.3 versus 98% with the same number of SLNs


*The score was assigned according to the following gradation: () = absence of the characteristic or negative evaluation, (+) = meets the characteristic or positive evaluation, (++) = complies being better; (+++) = it fulfils being superior. 99mTc = 99mTc-nanocolloid albumin; ICG = indocyanine green; NIR = near-infrared electromagnetic spectrum. Reference source: Papadia et al. [36].*

#### **Table 2.** *Characteristics of tracers.*

per patient and a tendency for the SPIO tracer to identify more metastatic SLNs, although further research is needed [34].

**Table 2** shows a comparison of the main characteristics of the most widely used tracers.

therefore, debatable results [30]. The study by Euscher et al. [81] compared two methods of ultrastaging by histological microsection, achieving increased detection of metastatic SLN in 32% of patients, with a mean metastasis size of 0.24–0.38 mm, with no differences in the detection rate by ultrastaging method. The algorithm proposed by the MSKCC consists of an initial assessment by H&E and, if negative, performing two adjacent 5-μm slices at two levels separated by 50 μm in the paraffin block, applying H&E staining and pan-cytokeratins AE1/AE3 in each slice [82]. Holloway et al. [48] performed three slices per level, two of which were then stained with H&E and one with AE1/AE3. Other authors have performed four levels with six slices at 40 μm intervals (levels 1 and 2 with H&E and levels 3 and 4 with AE1/AE3) or five levels (levels 1, 3 and 5 with H&E and 2 and 4 with AE1/AE3) [30]

Cytokeratin-19 (CK-19) is a protein of the intermediate filament responsible for the structural integrity of epidermal epithelial cells, which in normal conditions is not expressed in the lymphatic tissue and is expressed abnormally in more than 90% of cells by EC [83, 84]. CK-19 is a biomarker directly related to the capacity for tumour dissemination in EC, with high sensitivity and a capacity for discriminating between metastatic and nonmetastatic lymph nodes or areas of lymphovascular

Ultrastaging is a more complex procedure, requiring significant dedication, and has the added risk of high intraobserver and interobserver variability. The diagnostic categories of the American Joint Committee on Cancer (AJCC) are applied for breast cancer, with the following classifications for SLN: negative (<200 individual tumour cells or tumour cell aggregates <0.2 mm in size, including the presence of isolated cytokeratin-positive tumour cells [ITC]), micrometastatic (size ≥0.2 and <2 mm) (μM) or macrometastatic (>2 mm) (MM) [86]. The term low tumour

The ultrastaging of SLN has improved the validity of the technique and detects an additional 5–15%, with a high rate of low-volume lymph node disease (approximately 50% of patients with metastatic SLN), which would not be identified with the conventional technique. Ultrastaging represents an overall mean increase of

*The SLN algorithm for surgical staging of endometrial cancer. Obtained from NCCN Guideline in Endometrial Carcinoma, Version 4.2019: 'Principles of evaluation and surgical staging when SLN mapping is used, Figure 4: The SLN algorithm for surgical staging of endometrial cancer'. SLN = sentinel lymph node;*

25% (range, 10–60%) in detecting metastatic lymph nodes [80, 84].

(**Figure 1**).

invasion [84, 85].

**Figure 1.**

**185**

*LND = lymph node dissection.*

volume includes the ITC and μM categories.

*Role of Sentinel Node Biopsy in Endometrial Cancer DOI: http://dx.doi.org/10.5772/intechopen.89949*
