The immunohistochemical detection of
antigens in archival tissue sections has been hampered by the poor reactivity of certain
polypeptides in 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, retrospective, clinicopathologic studies of pediatric
primitive neuroectodermal tumors (
PNETs), also known as
medulloblastomas. We report our experience with a method of
antigen retrieval which greatly enhanced the immunohistochemical detection of neuronal and glial
intermediate filament proteins,
retinal S-antigen (RSA), and the
proliferating cell nuclear antigen (
PCNA) in archival,
paraffin-embedded,
formalin or Bouin's-fixed, pediatric
brain tumors, particularly
PNETs. The technique involves 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 microwave oven. The specificity of staining was consistent with known cell and tissue specificities of the well-characterized
monoclonal antibodies used and there was minimal background.
Synaptophysin (SYN) staining was unaffected by heating and immunoreactivity of the low affinity
nerve growth factor (p75NGFR) and the
neural cell adhesion molecule (
NCAM) were lost. The enhanced detection of neuronal and glial
antigens in routinely prepared,
formalin-fixed, archival material should facilitate large retrospective clinicopathologic studies designed to assess the prognostic implications of differentiation in
PNETs and to better understand the biology of these
tumors.