[Detection of Leu-M1 immunoreactivity in brain tissue and brain tumors]

Immunohistochemical investigations were made of 170 tumours of the central nervous system, using anti-Leu-M1, with electron microscopy being used on 22 of them. At least focal Leu-M1 positive reactivity was established from 10 in 24 astrocytomas, four in 22 oligodendrogliomas, and 9 in 15 ependymomas. Unambiguous Leu-M1 positivity was recorded from 54% of Grade I gliomas and 20% of Grade II gliomas. Other malignant primary tumours of neuroepithelial origin as well as all meningiomas and neurinomas proved to be Leu-M1 negative. However, severe immunopositivity was exhibited in all cases by reactive cerebral tissue adjacent to tumours. Three of four carcinoma metastases were Leu-M1 positive. Investigations, using electron microscopy, have clearly shown that MMA positivity in reactive brain is associated primarily with extracellular space and with plasma membranes of gliocytes. No products of immune reaction were identified, on the other hand, not even ultrastructurally, from neoplastically dedifferentiated cells of anaplastic neuroepithelial tumours. This is likely to suggest that neoplastically transformed gliocytes are no longer capable of expressing lacto-N-fucopentose III. It has proved helpful in distinguishing between the benign and malignant nature of a tumour. More observations along those lines might contribute to more knowledge on dedifferentiation of gliocytes. Also, in electron microscopy, MMA positivity of carcinomas proved to be associated with glycocalyceal material.