Overview of Immunocytochemical Approaches to the Differential Diagnosis of Tumors: Diagnostic Applications in the Clinical Laboratory

In 1974, the presence of intracytoplasmic immunoglobulins in plasma cells was demonstrated in routinely processed paraffin tissue (the mainstay of diagnostic pathology) using an immunoperoxidase technique (1). This new capability has introduced the surgical pathologist to a technique that can aid him or her in reaching a diagnosis on already available material, including cytological smears and touch preps, frozen sections, and paraffin-embedded tissues fixed in formalin, ethanol, and other fixatives (see Table 1 and Chapter 9 –Chapter 13 ). This novel approach of combining the sensitive and specific antibody-antigen reaction with the morphologic interpretation rendered by the experienced trained eye of the pathologist marks probably the most important advance in the world of diagnostic pathology in the last 20 years.