STUDIES OF CHILDHOOD BRAIN-TUMORS USING IMMUNOHISTOCHEMISTRY AND MICROWAVE TECHNOLOGY - METHODOLOGICAL CONSIDERATIONS

The immunohistochemical detection of antigens in archival tissue secti ons has been hampered by the poor reactivity of certain polypeptides i n conventional formalin-fixed, paraffin-embedded material. For example , the poor reactivity of neurofilament proteins (NFPs) in surgical and autopsy specimens has been a major drawback of previous large, retros pective, clinicopathologic studies of pediatric primitive neuroectoder mal tumors (PNETs), also known as medulloblastomas. We report our expe rience with a method of antigen retrieval which greatly enhanced the i mmunohistochemical detection of neuronal and glial intermediate filame nt proteins, retinal S-antigen (RSA), and the proliferating cell nucle ar antigen (PCNA) in archival, paraffin-embedded, formalin or Bouin's- fixed, pediatric brain tumors, particularly PNETs. The technique invol ves adding a single brief step to an established avidin-biotin complex (ABC) immunohistochemical protocol (Vectastain Elite Kit). This step involves boiling tissue sections in distilled water for 5 min in a mic rowave oven. The specificity of staining was consistent with known cel l and tissue specificities of the well-characterized monoclonal antibo dies used and there was minimal background. Synaptophysin (SYN) staini ng was unaffected by heating and immunoreactivity of the low affinity nerve growth factor (p75NGFR) and the neural cell adhesion molecule (N CAM) were lost. The enhanced detection of neuronal and glial antigens in routinely prepared, formalin-fixed, archival material should facili tate large retrospective clinicopathologic studies designed to assess the prognostic implications of differentiation in PNETs and to better understand the biology of these tumors.