AgNOR staining may reflect the growth potential of pilocytic astrocytomas.

The value of AgNOR staining as a tumor biological marker was tested in 26 children with pilocytic astrocytomas (20) and fibrillary astrocytomas (6). All patients were surgically treated and then followed up by periodic MRI or CT scans. Follow-up ranged from 8 to 84 months, with a mean of 44 months. AgNOR expression was determined by using semi-automated computer-assisted surface area measurements. AgNOR values ranged from 1.4 to 81.4 microm(2) per cell, with a mean of 26.6 and a median of 15.2. The median value was taken as a "cut-off" score separating two groups of patients with low and high AgNOR scores. Of the 13 patients in the low scoring group, 8 had total resections without recurrence, 3 had stable residual tumors, 1 had regressing residual tumor after irradiation and 1 had a recurrence 5 years after neuroradiologically complete resection of a fibrillary astrocytoma. In the group with high AgNOR scores only 2 patients had total resections without recurrence; 5 had stable residual tumors and 6 had residual tumors that showed progression, all within 1 year after surgery. Among the patients with classic juvenile pilocytic astrocytomas of the cerebellum 7 had residual tumor, which progressed in 2 patients, both of whom had high AgNOR scores. Among 7 patients with optic/hypothalamic tumors the 3 with rapidly progressing tumors all had very high AgNOR scores. The determination of AgNOR expression might be helpful in selection of patients with residual tumor after surgery, who may benefit from additional chemotherapy or (stereotactic) radiation therapy.