Immunoperoxidase technique in histopathology: applications, methods, and controls.

The macroscopic and microscopic morphology of a lesion is the basis of histopathological diagnosis. Conventional 'special ' stains are of value in diagnosis but they lack the specificity of immunological reagents. Thus the demonstration of immunoreactive calcitonin in a possible medullary carcinoma of the thyroid is more useful than the demonstration of argyrophilia by a Grimelius stain; similarly, an immunochemical stain for immunoglobulin in plasma cells or lymphomas of B-cell lineage is more conclusive than the pyroninophilia of ribosomal RNA shown by methyl green pyronin. For precise pathological classification we may need to use functional criteria in addition to morphology. Many cell products are readily demonstrable in routinely