Cd. Katsetos et al., LOBAR PILOCYTIC ASTROCYTOMAS OF THE CEREBRAL HEMISPHERES .2. PATHOBIOLOGY - MORPHOGENESIS OF THE EOSINOPHILIC GRANULAR BODIES, Clinical neuropathology, 13(6), 1994, pp. 306-314
This study provides new immunocytochemical observations on the so-call
ed eosinophilic granular bodies (EGBs), seen predominantly (but not ex
clusively) in pilocytic astrocytomas. Using combined immunohistochemic
al and immunoelectron microscopic approaches on formalin-fixed, paraff
in-embedded tissues, we have demonstrated that (1) EGBs exhibit pronou
nced reactivity with antibodies to serine protease inhibitors alpha-1-
antichymotrypsin and alpha-1-antitrypsin; by immunoelectron microscopy
, the reaction product is localized either in the form of diffuse floc
cular densities, or larger conglomerates of amorphous, globular materi
al; (2) an antiserum to ubiquitin-protein conjugates, codistributes in
the EGBs at the light microscopic level, while ultrastructurally is e
ither localized in diffuse, finely granular deposits, and/or fragmente
d filamentous particles; and (3) that a monoclonal antibody to beta-am
yloid precursor protein (beta-APP) stains smaller EGBs. The detection
of serpin-like and beta-APP-like staining in EGBs may be a reflection
of acute phase reactant activity in response to tumor-produced proteas
es. We postulate that EGBs contain complexes of serpins and hitherto u
nknown protease(s), which are in turn probably degraded via ubiquitin
mediated mechanism(s). Although EGBs typify pilocytic astrocytomas, th
ey may be exceptionally present in malignant astrocytomas, calling for
cautious interpretation of their biologic as well as prognostic impor
t.