Lymphoma 1987. An interim approach to diagnosis and classification

When immunophenotyping is used for diagnosis, it is essential to use panels of antibodies, rather than a single marker for a specific tumor type. There is virtually no single marker that is absolutely diagnostic and completely reliable for any particular neoplasm. For the most important clinical differential diagnoses--reactive versus neoplastic lymphoid lesions and lymphoma versus nonlymphoid tumor--relatively simple panels of antibodies are usually sufficient. In the former situation, immunoglobulin heavy and light chains (G, M, kappa, lambda) and a pan-T-cell antibody (Leu-4) will usually provide the answer. For the latter circumstance, kappa and lambda, a pan-leukocyte antibody, a pan-B-cell (B1), and a pan-T-cell antibody (Leu-4) along with cytokeratin constitute the initial panel. Further subclassification of lymphomas and leukemias can proceed using other antibodies as indicated in the preceding specific sections on the lymphomas. The use of specific antibodies for nonlymphoid tumors will be dictated by the morphologic appearance of the tumor. These may be used as a second panel if the initial screening does not establish a diagnosis of lymphoma. Performing and interpreting immunohistologic studies requires experience, and probably should not be attempted by laboratories that do not encounter a large number of lymphomas. Frozen tissue can be obtained and stored at -20 degrees for a few days; if immunohistologic studies are deemed necessary, the frozen tissue can be sent on dry ice to a reference laboratory. In preparing biopsy specimens for immunohistologic studies, and in interpreting the results of these studies, it is necessary to bear in mind the fact that morphology remains the most important tool for the diagnosis and subclassification of hematologic neoplasms. Obtaining tissue for marker studies should not be permitted to interfere with adequate morphologic examination. Similarly, artifacts and technical problems can occasionally lead to misleading results; the immunohistologic studies must be interpreted in light of the case as a whole, and should never be allowed to contradict common sense.