Table 2.

summary of reviewed biomarkers for SLN positivity.

Biomarker	Rationale	Sample	Results
VEGFR-3 Toberer et al. [33]	Involved in the stimulation of lymphangiogenesis	58 patients	-independent predictor of SLN positivity (ss) -VEGF-A highly expressed in the tumour tissue of SLN-positive patient (ss) but not an independent predictor of SLN positivity
Tetraspanin CD9 Lucarini et al. [37]	Transmembrane protein, key role in tumor progression Both suppressor and promoter of metastases, depending on the status of the cell membrane and vesicular structures	140 patients Melanocytic nevus 20 Primary melanoma 120 -<1 mm (thin) 24 -1.1–4 mm (intermediate) 56 ->4 mm (thick) 40	-CD9 not expressed in thin melanomas -CD9 reappears in 46% of intermediate and thick melanomas (near or within blood or lymphatic vessels); all of these melanomas showed a positive SLN -CD9 may be an excellent biomarker for assessing SLN status
LYVE-1 Doeden et al. [47]	LYVE-1 selective marker of lymphatic vessels	94 patients	-if LVI associated with intratumoral lymphatic vessels, increased SLN status prediction (positive predictive value 80%, negative predictive value 72%) [46]
D2-40 Fohn et al. [48]	D2-40 endothelial marker (podoplanin) In combination, better histological definition of LVI	158 patients Primary melanomas ≤ 2.0 mm	-D2-40 alone to assess LVI in ≤2 mm melanoma, good positive predictive ability (85.7%) for positive SLN [47]
31-GEP Vetto et al. [55]	Gene expression profile test, (markers for cell migration/chemotaxis/metastasis, secretory molecules, adhesion, lymphocyte invasion, transcription factors, differentiation/proliferation structural proteins and surface receptors) Identifies high-risk (>5%) patients, candidates for SLN	690 patients (total validation cohort, retrospective) staged I–III follow-up median 7 years 1421 patients (prospectively-tested)	-new class identification: class 1, low risk of SLN positivity -class 2, high risk (>5%) of SLN positivity -possibility of avoiding SLN in low-risk patients, reducing costs and overtreatment -validated method proposed by DecisionDx-Melanoma [56]

Vascular endothelium growth factor receptor-3 (VEGF), statistically significant (ss), lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), lymphovascular invasion (LVI), sentinel lymph node (SLN), and gene expression profile test (31-GEP).