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.