Fluorescence in situ hybridization for chromosome 14q deletion in subsets of meningioma segregated by MIB-1 labelling index.

Abstract

To correlate histopathological grading of meningiomas segregated into subgroups based on the MIB-1 labelling index (MIB-1 LI) with chromosomal loss of 14q using fluorescence in situ hybridization (FISH). Retrospective study conducted in a tertiary hospital. Forty-six cases from January to December 2011 were segregated into 5 categories based on the MIB-1 LI. Slides were reviewed to ascertain the grade. Immunohistochemical staining for MIB-1 was performed using a Ventana Benchmark XT autostainer. Commercially available FISH paraffin pretreatment kit and SpectrumOrange fluorophore labelled probe were used. The Statistical Package for the Social Sciences version 16.0 for Windows was used for statistical analysis. There were 21 World Health Organisation (WHO) grade I, 24 grade II, and 1 grade III meningiomas. There was a statistically significant difference between the mean duration of symptoms, maximum dimension, and the MIB-1 LI of grade I and grade II meningiomas. 33.3% grade I cases showed 14q deletion, compared to 84% of grade II and III meningiomas. Histologically, hypercellularity, small cell formation, prominent nucleoli, and sheet-like growth were significantly associated with 14q deletion. All brain invasive meningiomas had 14q deletion. As MIB-1% increased, the prevalence of deletions was significantly higher. The mean MIB-1 of the 7 grade I meningiomas that had 14q deletions was 8.86 ± 1.95% when compared to 4.14 ± 1.35% for those without 14q deletions. A strong association existed between histologic grade, MIB-1 LI, and the presence of chromosome 14q deletion. Association of high MIB-1 LI with 14q deletions, even in meningiomas with a Grade I histology, defines a distinct subset of benign meningiomas.