Role of Pathology and Immunohistochemistry in the New Era Of Molecular Therapy

The modern practice of pathology entails increasing involvement with management of cancer patients. Pathologists are often faced with clinical and research involvements that obligate them to search for prognostic and therapeutic markers on patients’ tumor samples. A practical example would be the detection of HER2-neu in breast cancer which has revolutionized the use of prognostic-therapeutic immunohistochemistry (IHC) in the practical management of patients. Numerous other markers and proliferation pathways have recently been elucidated in many human cancers including pediatric cancers. Although most of these markers are being detected by conventional molecular techniques, IHC methods, routinely practiced in histopathologic laboratories, are being employed at an increasing pace. Since most of these proliferation markers are also the targets of new specific therapy, their positive identification often correlates with the appropriateness of that specific therapy and with other parameters that can gauge the patient’s prognosis. A good example is the identification of epidermal growth factor receptor by IHC in the patient’s lung tumor as an indicator of the tumor responsiveness to “Gefitinib”. Such potential application of immunohistochemistry in patients’ care necessitates adequate standardization of this technique to optimize patients’ management, since erroneous results can lead to erroneous management of patients with cancer. These facts will initiate a new role for pathology laboratory departments to provide a stronger impact on patients’ managements.