Immunocytochemistry and the Pathological Diagnosis of Cerebral Tumours

Abstract

Traditionally, the diagnosis of cerebral tumours has been based upon histological morphology and the resemblance of tumour cells to normal tissues (1). With the introduction of immunocytochemistry, it became possible to identifiy cellular elements in normal brain and other tissues by the presence of specific intracellular elements such as intermediate filaments, other cell proteins and cell products (Table 1) or by the expression of cell surface antigens (2). However, it also became clear that, as a reflection of changes in the DNA of tumour cells, normal cell components or surface antigens of the proposed cell of origin were not always appropriately expressed by the tumour cells (3). Some neoplastic cells retain appropriate marker proteins, whereas, in other tumours, the cells lose marker proteins or even gain markers that are inappropriate for the apparent cell of origin. The main use of immunocytochemistry in the diagnosis of cerebral tumours lies in 3 main areas:

• a) Definition of the cell of origin ofa tumour but taking into the account the loss or gain of marker proteins by tumour cells.

• b) Identification of normal and reactive nervous tissue cells and their relationships to tumour cells. Immunocytochemistry has supplemented or even replaced the use of capricious silver stains and dye techniques for light microscopy and has reduced the need for electron microscopy in tumour diagnosis.

• c) Detection of inflammatory cells and lymphocyte subsets within tumours and the use of similar techniques for the diagnosis and classification of lymphomas.