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Abstract
Background Many sentinel lymph node (SLN) ultrastaging protocols for endometrial cancer exist, but there is no consensus method.
Objective This study aims to develop guidelines for size criteria in SLN evaluation for endometrial cancer, to determine whether a single cytokeratin AE1:AE3 immunohistochemical slide provides sufficient data for diagnosis, and to compare cost efficiency between current and limited ultrastaging protocols at a large tertiary care institution.
Methods Our current SLN ultrastaging protocol consists of cutting two adjacent paraffin block sections at two levels (L1 and L2), 50 μm apart, with two slides at each level stained with hematoxylin and eosin and cytokeratin AE1:AE3 immunohistochemistry. We retrospectively reviewed digitized L1 and L2 slides of all positive ultrastaged SLNs from patients treated for endometrial cancer between January 2013 and January 2020. SLN diagnosis was defined by measuring the largest cluster of contiguous tumor cells in a single cross section: macrometastasis (>2.0 mm), micrometastasis (>0.2 to ≤2.0 mm or >200 cells), or isolated tumor cells (≤0.2 mm or ≤200 cells). Concordance between L1 and L2 results was evaluated. Cost efficiency between current (two immunohistochemical slides per block) and proposed limited (one immunohistochemical slide per block) protocols was compared.
Results Digitized slides of 147 positive SLNs from 109 patients were reviewed; 4.1% of SLNs were reclassified based on refined size criteria. Complete concordance between L1 and L2 interpretations was seen in 91.8% of SLNs. A false-negative rate of 0%–0.9% in detecting micrometastasis and macrometastasis using a limited protocol was observed. Estimated charge-level savings of a limited protocol were 50% per patient.
Conclusion High diagnostic accuracy in SLN interpretation may be achieved using a limited ultrastaging protocol of one immunohistochemical slide per block and linear measurement of the largest cluster of contiguous tumor cells. Implementation of the proposed limited ultrastaging protocol may result in laboratory cost savings with minimal impact on health outcomes.
- sentinel lymph node
Data availability statement
Data are available upon reasonable request. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
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Data availability statement
Data are available upon reasonable request. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Footnotes
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Contributors Conception and design: SC, LE. Provision of study material or patients: NRA-R, ML, JM. Collection and assembly of data: NRA-R, ML, JM, SC, BT-C, OA, EK. Data analysis and interpretation: SC. Manuscript writing: SC, LE. Final approval of manuscript: all authors. Guarantor: SC.
Funding The study was supported in part by the National Institutes of Health/National Cancer Institute Cancer Center support grant (P30 CA008748).
Competing interests ML reports being an ad hoc speaker for Intuitive Surgical, Inc., has consulted for Medtronic, and has served on the advisory boards of Ethicon/Johnson & Johnson and Immunogen. NRA-R reports grant funding from GRAIL paid to the institution. The other authors declare no conflict of interest.
Provenance and peer review Not commissioned; externally peer reviewed.
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