1p And 19q Fish

What is 1p/19q deletion by FISH test?

1p/19q deletion by FISH is a cytogenetic test using fluorescent DNA probes targeting 1p36 with control 1q and 19q13 with control 19p on tumor nuclei to determine whether there is deletion of 1p and 19q, reported as intact, single‑arm loss, or co‑deletion.

Why consider 1p/19q deletion by FISH test?

• Confirms oligodendroglioma when taken with IDH mutation and appropriate histology, which is essential for WHO CNS tumor classification and accurate diagnosis.

• Predicts better prognosis and higher sensitivity to alkylating chemotherapy and radiotherapy in anaplastic and diffuse oligodendrogliomas compared with astrocytic gliomas.

Who should get tested for 1p/19q deletion by FISH test?

• Suspected diffuse glioma with oligodendroglial features on imaging or histology, especially tumors previously labeled oligodendroglioma/oligoastrocytoma where definitive classification impacts care.
• Confirmed IDH‑mutant diffuse glioma where establishing 1p/19q codeletion is required to diagnose oligodendroglioma per current WHO criteria.
• Newly biopsied or resected adult low‑grade or anaplastic gliomas to refine prognosis and guide chemotherapy/radiotherapy planning.
• Cases with ambiguous histology where distinguishing oligodendroglioma from astrocytoma will change treatment strategy, follow‑up, and counseling.
• Any brain tumor workup where confirming 1p/19q codeletion will inform prognosis and predict alkylating chemotherapy sensitivity.

More Information

OTHER NAMES: 1p/19q codeletion FISH, 1p and 19q deletion analysis by FISH, Oligodendroglioma 1p/19q FISH test

1p/19q codeletion is the complete loss of the short arm of chromosome 1 (1p) and the long arm of chromosome 19 (19q) in a tumor. This genetic alteration is a defining characteristic of oligodendroglioma, a type of primary brain tumor, and is crucial for its diagnosis, prognostication, and predicting a patient's response to therapy. The codeletion is a result of a prior translocation between chromosome 1 and chromosome 19, followed by the loss of the involved chromosome segment.