Introduction

Abstract

Although special techniques have been applied for more than a century to aid the diagnosis of pathology specimens, it is only within the past 10–20 years when the field of ancillary techniques has exploded to the current levels. From the beginning of histology and pathology, morphologists have used a wide range of special techniques such as silver stains to detect the presence of axons, colloidal iron stain to detect mucin deposits in the dermis, or Steiner stain to detect spirochetes. During the 1960 and 1970s, electron microscopy allowed examination of the subcellular structures to detect, among others, the capsids of viruses, organelles associated with a particular neoplasm (Birbeck granules in Langerhans cell histiocytosis), or alteration of the basement membrane area in the different subtypes of epidermolysis bullosa. Since the 1980s immunohistochemistry has become widely used to detect antigens, with applications to neoplastic (e.g., differentiation between Paget disease and melanoma), inflammatory (differentiation among the different subtypes of cutaneous immunobullous diseases), and infectious conditions (detection of spirochetes in cutaneous lesions of syphilis). In a sense, we can consider immunohistochemistry as an early “molecular” technique since it allows the detection of specific antigens (i.e., “molecules”).