Chromosomal aberrations in chordoid meningioma - An analysis

Chordoid meningiomas (CMs) are a rare subgroup of tumors, accounting for approximately 0.5% of all meningiomas. These tumors correspond to World Health Organization (WHO) Grade II lesions and behave aggressively, with an increased likelihood of recurrence. There are only two studies that have described the genetic alterations in CMs. While a majority of meningiomas are known to have deletion at many chromosomal loci such as 22q, 18p, 14q, and 1p, which are found to be associated with initiation, progression, and malignancy of these tumors, these have not yet been studied in CMs. Thus, our aim was to evaluate the status of these four chromosomal aberrations in CMs and correlate the findings with the clinical outcome of patients.

A total of 15 cases of CM operated over a period of 12 years from 2001 to 2013 were analyzed. The archival paraffin blocks were retrieved and sections were subjected to locus-specific fluorescent in situ hybridization (FISH) using 22q12.2, 18p11.3, 14q32.2, and 1p32.3 probes. Immunohistochemistry (IHC) was done on all cases using MIB-1, vimentin, glial fibrillary acidic protein (GFAP), and epithelial membrane antigen (EMA) antibodies.

All cases had characteristic features of CM, and were positive for EMA and vimentin and negative for GFAP. The mean labeling index for MIB-1 was 2.7 ± 0.8%. Of the 15 cases, 5 cases showed recurrence with a median follow-up period of 28 months. Patients who underwent Simpson's grade I excision did not show any relapse of the tumor. Of the 5 recurrent cases, 4 had complete deletion of all four chromosomal loci. Among the 10 nonrecurrent cases, 9 (90%) showed either partial deletion or an intact status.

This is the first study to evaluate the combined chromosomal status of 22q, 18p, 14q, and 1p in CMs. Our study shows that there was a higher propensity of recurrence in tumors, even with complete excision, with complete deletion in all four chromosomal loci.