ALK Gene Mutation and ALK Protein Expression in Advanced Neuroblastoma and Potential Value in Risk Stratification in Fine Needle Aspiration Biopsy Samples

Abstract

Objective:Anaplastic Lymphoma Kinase ( ALK) gene gain-of-function point mutation leading to its overexpression has recently been identified and targeted in neuroblastoma (NB). We evaluated ALK gene mutation and its protein expression in cases of NB on fine needle aspiration biopsy (FNAB). Material and Methods: FNAB diagnosed cases of NB (n=56) were evaluated with cell blocks for MYCN amplification and ALK protein expression by Fluorescence in-situ hybridization and immunocytochemistry respectively. MGG stained smears (n=22) were used for Next generation sequencing (NGS) analysis using the Cancer Hotspot panel (version2) on Ion Torrent S5 platform. Staging and risk assignment as per International Neuroblastoma Risk Group (INRG) was performed and managed. All the parameters were correlated with overall survival. Results: ALK protein showed cytoplasmic expression in 65% of cases and did not correlate with MYCN amplification (p=0.35), INRG groups (p=0.52), and overall survival (p=0.2); however, ALK+ poorly differentiated NB showed better prognosis (p=0.02). ALK negativity was associated with poor outcome by Cox proportional hazard model (hazard ratio=2.36). ALK gene, exon 23 missense mutations (F1174L) were seen in 2/21 cases with an allele frequency of 8% and 54%. Both these cases showed ALK protein expression and died of disease within 1 and 17 months respectively. A novel IDH1 exon 4 mutation was also detected. Conclusion: ALK expression is a promising prognostic as well as a predictive marker in advanced NB along with traditional prognostic parameters. FNAB smears are suitable for NGS and ALK gene mutation confers a poor prognosis.