Professional hub · melanoma · 2026
SLNB in melanoma: procedural and pathology quality standards
From indication and lymphatic mapping to grossing, serial levels, immunohistochemistry and pN staging. The central principle is that SLNB quality is determined by the entire multidisciplinary process, not a single step.
Evidence rule: Ukrainian Unified Clinical Protocol No.1064 is the national practice framework. EORTC, CAP, RCPA, ESMO and ASCO/SSO are used to add international technical detail. Where protocols use different sectioning schemes, that variation is stated explicitly rather than inventing one universal number of levels.
Indications
Plan before wide excision changes lymphatic drainage
SLNB pathologically stages clinically node-negative regional basins. Indications depend on the risk of occult nodal disease.
| Situation | Ukraine, protocol No.1064 | ESMO / ASCO-SSO | Practical point |
|---|---|---|---|
| pT1a <0.8 mm without ulceration | Not routinely recommended. | Not routine; may be discussed in selected high-risk situations. | Do not turn SLNB into an automatic procedure for thin melanoma. |
| pT1b | Recommended in the national protocol. | ESMO: discuss with the patient. | Shared decision-making with risk/benefit discussion. |
| Clinically N0, ≥1 mm | Used for pathological staging. | ESMO recommends for T2a and above. | Core SLNB setting in the absence of clinical nodal disease. |
| Wide local excision | SLNB should be performed together with WLE to avoid disturbing lymphatic drainage. | International practice likewise plans mapping before disruption of lymphatic pathways. | Timing is part of procedural quality. |
Lymphatic mapping
Sentinel-node identification methods in the current Ukrainian protocol
For sentinel-node detection, Ukrainian Unified Clinical Protocol No.1064 explicitly provides two approaches: technetium-based radionuclide mapping or indocyanine green (ICG). The aim is to reproduce the true lymphatic drainage pathway and identify all sentinel nodes.
| Method | Practical role | Key principle |
|---|---|---|
| Technetium-based radionuclide mapping | Preoperative lymphatic mapping and intraoperative node identification using a gamma probe. | Defines draining basins and sentinel nodes according to functional lymphatic drainage. |
| Indocyanine green (ICG) | Fluorescence-guided intraoperative navigation. | Also explicitly named in the current Ukrainian protocol as a method of sentinel-node detection. |
Regarding blue dye: it is not listed in Ukrainian Protocol No.1064 among the methods of sentinel-node detection. International literature may describe blue dyes as adjunct tracers, but they should not be presented as a stand-alone equivalent of complete lymphatic mapping.
Quality questions: were all draining basins defined? Were all sentinel nodes identified and removed according to the chosen method? Was each node labelled separately for pathology?
Grossing and sectioning
“One block - one section” is not an adequate sentinel-node protocol
The aim is to examine enough tissue volume that a small metastatic deposit is not left between two examined planes.
| Protocol | Gross/microscopic handling |
|---|---|
| Ukraine, No.1064 | Paraffin-block tissue pieces ≤2-3 mm; serial sections at at least 3 levels; H&E + IHC. |
| RCPA | Slice sentinel nodes at approximately 2-mm intervals along the long axis; submit all sections; step sections and IHC are used for assessment. |
| EORTC 2019 | Standardized multilevel sectioning; spacing is adapted to node size/shape. Minimum intervals may be around 50 μm, while other validated protocols use wider spacing. |
| CAP | Does not impose one universal numeric level algorithm for every sentinel node; adequate tissue assessment and complete reporting remain central. |
Avoid presenting as a universal rule: “everyone requires six levels at 50 μm” or “3-6 levels at 50-250 μm”. A more defensible formulation is: Ukrainian minimum ≥3 levels; the exact number and spacing follow a validated laboratory protocol.
Immunohistochemistry
IHC increases sensitivity but does not replace morphology
The Ukrainian protocol requires at least three melanocyte-specific antibodies. Examples include SOX10, S100, HMB45, Melan-A, tyrosinase and MITF.
| Marker / situation | Practical interpretation |
|---|---|
| SOX10 / S100 | Sensitive melanocytic markers, but may also be positive in nodal nevi. |
| Melan-A | Supports melanocytic differentiation; benign nevus cells may also stain. |
| HMB45 | May help with distinction, but sensitivity varies. |
| PRAME / p16 | Useful adjuncts in difficult cases; neither is sufficient alone. Negative PRAME does not exclude melanoma. |
| Isolated IHC-positive cell | Without morphologic features of melanoma, should not automatically render the sentinel node positive. |
Pathology report
More than “metastasis present / absent”
The Ukrainian protocol already requires multiple quantitative and topographic fields; EORTC adds further detail on microanatomic tumour burden.
- Sentinel-node location
- Regional basin / side.
- Number of sentinel nodes
- How many nodes were actually examined.
- Number positive
- How many contain confidently identified melanoma metastasis.
- Number and location of deposits
- Subcapsular, parenchymal, combined or other pattern.
- Largest deposit
- Maximum dimension in millimetres.
- Extranodal extension
- Present/absent.
- Nodal nevus cells
- EORTC recommends noting them, particularly in difficult differential diagnoses.
- Method of detection
- H&E and/or IHC interpreted in morphologic context.
Quality assurance
A false-negative result can arise at different stages
False-negative SLNB should not be reduced to pathology alone. Failure may occur during mapping, surgery or laboratory evaluation.
Nuclear medicine / mapping
An unrecognized basin, interval node or incomplete lymphatic map.
Surgery
Failure to remove one of the sentinel nodes or misinterpretation of navigation.
Pathology
Insufficient sectioning, a missed small deposit or incorrect IHC interpretation.
2025 meta-analysis: 14 studies, 8,447 patients, pooled sensitivity about 85% (95% CI 80-88%); estimated NPV 93-97% depending on pretest risk. These are characteristics of the entire SLNB process, not pathology alone. Thirteen of 14 studies were at high risk of bias, so the figure must not be translated into “15% of all negative SLNBs are wrong”.
Open clinical figures
Examples of diagnostic pitfalls
External figures are used only when reuse rights are explicit. The key pathology figures here are CC BY.
Additional open resource: Marone et al. published CC BY lymphoscintigraphy examples of unusual/interval drainage pathways in melanoma. Open source →
Primary sources
Evidence backbone
The page separates the Ukrainian regulatory framework, guideline recommendations and observational/meta-analytic evidence.
Ukraine Unified Clinical Protocol No.1064, 2023National standard: indications, detection, ≥3 levels, H&E + IHC, ≥3 antibodies and report fields.EORTC updated pathology protocol, 2019Sectioning, IHC, microanatomic location, deposit number/size and nodal nevi.Scolyer, Gershenwald, Thompson, 2019Isolated IHC-positive cells without melanoma morphology should not automatically define a positive SLN.Nodal nevus vs metastasis review, 2025HMB45, PRAME, p16, SOX10, S100 and Melan-A in the differential diagnosis.BJS Open diagnostic accuracy meta-analysis, 202514 studies, 8,447 patients; sensitivity/NPV and risk of bias.SLN mapping technique meta-analysisComparison of mapping approaches and sentinel-node identification rates.RCPA sentinel-node cut-up manualMacroscopic handling and complete submission.Siarov et al., Frontiers in Medicine, 2024CC BY histology/IHC figures and diagnostic pitfalls.