Immunohistology in the identification of tumour types.

Recently developed immunohistological techniques coupled with the advent of the monoclonal antibody era have revolutionized diagnostic tumour pathology. The search for a tumour specific marker has not been fulfilled; however, judicious use of panels of antibodies recognizing tissue differentiation antigens has enabled separation of morphologically indistinct tumours where this was not previously possible. This same approach has proved useful for identifying site of origin in small tumour biopsy specimens, in aspirates of malignant cells from body fluids and in micrometastases. Lymphoma phenotyping is the field where the greatest advances have been made. This is because of the diverse range of antibodies available in this area and the widespread cooperation in characterizing and clustering these antibodies that has occurred at the three international workshops on leucocyte antigens. Less dramatic, but nevertheless appreciable advances have been made in the field of solid tumours, using antibodies to differentiation products or organ specific products to identify the site of origin of a carcinoma or sarcoma. The identification of consistent production of aberrant differentiation products also provides a promising approach to tumour identification. The recognition of changed antigenic phenotype in preinvasive neoplastic cells offers a means of early, more objective, diagnostic assessment of these lesions.