2026 – Abstract 14

by | Aug 13, 2026 | 2026 Abstracts

Category: Clinical Science

At the end of the session, participants will be able to:

  1. Describe the chromosome alterations which affect the grading of meningiomas according to WHO CNS5 and cIMPACT-NOW update 8
  2. Describe the diagnostic techniques available to detect these alterations.
  3. Propose an algorithm to implement such diagnostic testing in a cost-efficient manner

COI Disclosure:

None to disclose

Presenter

Dr. Gould – Neuropathologist
Hôpital de l’Enfant-Jésus du CHU de Québec – Université Laval, Quebec City

Peter V. Gould1, Stephan Saikali1, Claudie Paquet1, Juliette Fournier Loiselle2. 

1Service clinique d’anatomopathologie, CHU de Québec – Université Laval, Quebec City

2Faculté de medécine, Université Laval, Quebec City

Target Audience:
Pathologists

CanMEDS:
Medical Expert (the integrating role)
Scholar

Reliable detection of chromosome abnormalities in meningiomas by FISH and immunohistochemistry

Abstract

Chromosomal abnormalities described in meningiomas include loss of chromosome 9p21, loss of chromosomes 1p and 22q and gain of chromomosome 1q. Immunohistochemistry for p16 and MTAP has been suggested as a surrogate marker for loss of chromosome 9p21. We assembled a retrospective series of 165 patients to study these alterations by FISH and immunohistochemistry on tissue microarrays from the over 1000 meningioma patients operated at Hôpital de l’Enfant-Jésus between 01/2005 and 02/2025. 47 patients were less than 40, 14 patients were initially diagnosed with histologic grade 3 or high-grade subtypes, and 107 patients had tumours which recurred. Histologic grade and chromosomal alterations on FISH were prognostic for clinical outcome. Overexpression of p16 was prognostic for loss of chromosome 9p21 if present. Absence of MTAP expression showed a tendancy to predict loss of chromosome 9p21. Twelve patients aged less than 40 were reclassified but this did not influence clinical outcome since none of them relapsed. Twenty recurrences of grade 1 tumours were reclassified (15 from grade 1 to grade 2, 5 from grade 2 to grade 1) and 8 recurrences of grade 2 tumours were reclassified (3 to grade 1, 5 to grade 3). Of the 14 patients with high grade tumours, 5 were reclassified as grade 2. In our series, patients with recurrent meningiomas, or meningiomas with high-grade histology, benefit from molecular analysis. Patients less than 40 years old do not.