Background/aim: Cytogenetic profile of posterior uveal melanoma (mainly monosomy 3) is actually considered the most specific prognostic factor for uveal melanoma patients. Nevertheless, there is still no consensus on which cytogenetic analysis should be used, and there is still no long-term data about the safety of sampling procedure. The aims of this study were to evaluate (i) long-term safety and efficacy of in-vivo 25-gauge transcleral Fine Needle Aspiration Biopsy (FNAB) and (ii) predictive value of Fluorescent In-situ Hybridization (FISH) vs Multiplex Ligation-dependent Probe Amplification (MLPA) analysis for cytogenetic testing of posterior uveal melanoma.
Methods: One hundred thirty-nine consecutive patients affected by posterior uveal melanoma with tumour thickness > 3mm underwent in-vivo 25-G transcleral FNAB (through the tumor base) just before applying the I-125 active plaque. A double pass sampling was performed. Sampled material underwent both FISH (chromosome 3 and 6) and MLPA analysis using standard procedures. Follow-up examination, including A/B-Scan eye and orbit ultrasonography, was performed after 1 month and every 6 months thereafter. Follow-up was longer than 24 months.
Result: Follow-up was 54±16 months (range, 24-84 months). FNAB yielded sufficient material for FISH analysis in 117 cases (84.2%). Fifty-six cases had monosomy 3 (47.9%). No clinically relevant monosomy 3 heterogeneity was detected (double pass sampling). Chromosome 6 co-detection using FISH was performed in forty-four patients. Monosomy 3 and +6p resulted mutually exclusive in 40 cases (90.9%). Univariate Cox analysis showed metastatic disease to be strongly associated with monosomy 3 (p=0.005). No misclassification occurred in
low risk patients having both disomy 3 and +6p. MLPA was performed in twenty- four patients revealing monosomy 3 in thirteen cases (54%) (vs twelve cases classified by FISH) and a 3p14-q29 deletion in one case (4%) (classified as monosomy 3 by FISH). Considering this sub-group of twenty-four patients having both FISH and MLPA, nine patients (41%) developed metastatic disease during follow-up, including the case showing monosomy 3 only by MLPA. Patient with partial chromosome 3 deletion by MLPA is still alive without metastases. Due to FNAB procedure, tree patients developed transient, localized and self-limited subretinal haemorrhages after FNAB. Neither other short- and long-term complications nor extrascleral extensions were documented during follow up.
Conclusion: The use of 25-G transcleral FNAB appears a long-term safe and effective procedure for in-vivo cytogenetic testing of posterior uveal melanoma. Combined analysis of both arms of uveal melanoma bifurcated pathway (-3 and +6p) increase predictive value of FISH technique. MLPA allows obtaining more information than standard FISH in uveal melanoma prognostication. The biological and prognostic value of partial chromosome 3 deletion, as well as others subtle chromosomes alterations or complex MLPA results, remains unclear
