Test Details: Immunohistochemical testing is carried out on biopsy/resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody .Isocitrate dehydrogenase 1 is a metabolic enzyme. IDH1 is a useful immunohistochemical marker to differentiate low-grade astrocytoma from reactive gliosis, has potential as an independent prognostic marker and also helps in distinguishing primary from secondary GBM. IDH1/2 mutation may differentiate chondrosarcoma (mutation present) from chondroblastic osteosarcoma (mutation not present).