AgNOR- and PCNA-studies in astrocytomas of the optic nerve.

Nine pilocytic astrocytomas of the optic nerve were investigated with the AgNOR method and by immunohistochemistry with anti-PCNA antibodies. Four patients were male, 5 female (mean age 16.5 years, range 1-55 years). Seven pilocytic astrocytomas were low-grade tumors (grade I, WHO [2]), one tumor contained giant cells and prominent nuclei (grade II), the remaining tumor was anaplastic (grade III). In each case, 5 randomly chosen areas were investigated by light microscopy using objective 40. The PCNA staining index was defined as number of positive tumor cell nuclei divided by the total amount of tumor cell nuclei in the microscopic field. Tumors showing only one immunopositive cell nucleus at low magnification were considered to have a staining index below 0.1%. The staining index of the 7 grade I tumors was below 0,1%, the grade II tumor showed a staining index of 1%, and the anaplastic astrocytoma (grade III) demonstrated a 2.5% staining index. Investigations with the AgNOR method confirmed the above results of a low growth fraction in grade I-III grade astrocytomas of the optic nerve. Though low growth fractions have been reported in anaplastic astrocytomas and glioblastomas of the cerebrum, the low staining index in the anaplastic pilocytic astrocytoma of our series is remarkable: Instead of histological parameters like cellular and nuclear polymorphism and cellular density, the growth fraction could be a better parameter for the clinical course, which has in fact been benign in this case of an anaplastic pilocytic astrocytoma of the optic nerve.(ABSTRACT TRUNCATED AT 250 WORDS)