Oligodendroglioma (ODG) 1p/19q FISH

OVERVIEW

ODGs are aggressive tumours that have a peak incidence in the 5th and 6th decade with a slight male predominance. The most common site affected is the frontal lobe with patients presenting with seizures. 1p/19q loss is a recurrent abnormality in ODGs and results from an unbalanced translocation t(1;19)(q10;p10) resulting in the loss of the whole short arm of chromosome 1 and the long arm of chromosome 19. Smaller deletions have been reported but typically occur in glioblastomas. 

The presence of a co-deletion of 1p/19q is diagnostic of ODG in adults.  Tumours with 1p/19q co-deletion are associated with an increased survival relative to gliomas lacking this alteration and demonstrate improved therapeutic response to procarbazine-ccnu-vincrisine (PCV) chemotherapy.  

TEST REQUIREMENTS

  • Tumour block
  • One 4-6µm unstained section on positively charged slides for each FISH probe requested plus an additional unstained slide (if repeats are necessary)
  • H&E that matches the current block surface
  • The H&E should be circled with the area to sample for FISH analysis  –  multiple circles can be made and each circle should be larger than 10mm
  • For the circled area, in the space provided on the requisition, provide the tumour content (i.e. the proportion of nuclei in the circle that are tumour cells) and the tumour cellularity (i.e. the proportion of space occurred by nuclei).  NOTE: 10% tumour content is the minimum requirement for this assay.
  • Completed CGL requisition  – current requisitions can be found here: https://cancergeneticslab.ca/requisitions/

TURN-AROUND TIME

Results are reported within fourteen days from receipt of specimen and completed requisition form.  

RESULTS REPORTING

This FISH assay is performed to aid in the diagnosis of oligodendroglioma. Specimens are reported as Positive for a 1p/19q co-deletion or Negative for a 1p/19q co-deletion.

METHOD

FISH analysis is performed on the provided paraffin embedded tissue using two commercial probe sets (Vysis) to chromosome 1 (probes within 1p36 and 1q25) and chromosome 19 (probes within 19p13 and 19q13).

REFERENCES

  1. Cairncross JG, Ueki K, Zlatescu MC, et al. 1998  Specific genetic predictors of chemotherapeutic response and survival in patients with anaplastic oligodendrogliomas.  J Natl Cancer Inst. 90:1473-9.
  2. Ren X, Jiang H, Cui X, et al.. 2013 Co-polysomy of chromosome 1q and 19p predicts worse prognosis in 1p/19q codeleted oligodendroglial tumors: FISH analysis of 148 consecutive cases.  Neuro Oncol. 15:1244-50.
  3. Wesseling P, van den Bent M, Perry A.  2015  Oligodendroglioma: pathology, molecular mechanisms and markers. Acta Neuropathol. 129:809-27
  4. Reuss DE, Sahm F, Schrimpf D, et al.  2015  ATRX and IDH1-R132H immunohistochemistry with subsequent copy number analysis and IDH sequencing as a basis for an “integrated” diagnostic approach for adult astrocytoma, oligodendroglioma and glioblastoma.  Acta Neuropathol. 129:133-46.