Immunohistochemistry (IHC) - IDH1 Test

Immunohistochemistry (IHC)-IDH1 Test

This histopathological test is done for patients diagnosed with certain brain tumours called glioma. It helps in molecular detection of mutation (change in genetic sequence) in IDH1 (isocitrate dehydrogenase 1) gene in tumour tissue sample.IDH1 gene is also called R132.This test is called IHC IDH1 test.

Glioma are one of the common primary tumours of the central nervous system(brain and spinal cord).They are usually associated with dismal outcome. They arise from the glial cells (supportive cells) that surround the nerve cells. The various types of glioma are Oligodendroglioma, astrocytoma and ependymomas. The different types of glioma differ in their location, morphology, prognosis and clinical outcome.

The common symptoms associated with glioma are:

• Headache
• Nausea/vomiting
• Confusion
• Loss of memory
• Difficulty in movement and balance
• Bladder disturbances
• Visual disturbances
• Speech problems
• seizures

Why is Immunohistochemistry (IHC) IDH1 Test prescribed?

• The health care provider may prescribe this test in patients with glioma to know the prognosis of a particular tumour
• It also helps to provide better management of the condition by selecting appropriate therapy.
• This test helps in better risk stratification-differentiate high risk glioma from low risk glioma

IDH1 mutation is seen in grade2 diffuse glioma, grade 3diffuse glioma, Oligodendroglioma, anaplastic Oligodendroglioma, secondary glioblastomas, mixed oligoastrocytoma and has good prognosis.

IDH1 is seen rarely in pilocytic astrocytomas, primary glioblastomas and is absent in ependymomas.

Procedure and prerequisites

IHC IDH1 test is done on tumour biopsy tissue which is taken out by inserting a needle into the tumour through a small hole in skull. Tumour biopsy specimen taken for histopathological examination should be handled with utmost care and precautions without destroying it by various instruments. Pulling of the tissue should not be done. Tissue should not be put on dry gauze or gauze soaked with water. It should be immediately stored in an appropriate sized container containing 10%neutral buffered formalin (formaldehyde solution). The specimen should be totally immersed in formalin. It should not be freezed or put in ice cold saline. Container should be labelled properly with necessary details. Relevant clinical history/physical examination findings/radiological reports must be sent along with the sample. A properly filled requisition form must accompany the sample.