The diagnostic value of immunohistochemistry and silver impregnation techniques for characterization of normal, reactive and tumoral astrocytes.

Astrocytes represent a heterogeneous population of specialized glial cells responsible not only for accomplishing various important functions in the healthy nervous tissue, but also for reacting to all types of the central nervous system diseases and trauma. GFAP immunostaining is considered to be the most accurate of the routine techniques used for identifying astrocytes; however, silver impregnation techniques, which are inexpensive and approachable, might be a reliable alternative. The present research has brought into question and tried to assess the sensitivity and specificity of these classical methods for identifying and differentiating normal and reactive from tumoral astrocytes. Our study included 10 supratentorial gliomas specimens of various grade and two normal brain samples. We performed a histological study on consecutive seriated sections labeled using four methods: the immunostaining for GFAP (glial fibrillary acidic protein) and the three silver impregnation techniques: Ramón y Cajal, Bielschowsky-Cajal and Gömöri. For each tumoral case, two areas were examined: the tumoral parenchyma and the tumor borders (considered as reactive gliosis) and were both compared to healthy brain parenchyma; for each area, three microscopic fields were assessed and two parameters were recorded: a semi-quantitative score (the astrocytes' density) and a qualitative score (the color intensity). We used a complex statistical analysis in order to process the data and to compare the diagnostic value of silver impregnation techniques versus GFAP immunostaining (the reference method) in terms of tumoral grading and differentiating tumoral from normal and reactive astrocytes. Our results indicated that there data provided by both GFAP immunostaining and silver impregnation techniques were comparable.