The NBN (NBS1) gene belongs to a group of double-strand break repair genes. Mutations in any of these genes cause genome instability syndromes and contribute to carcinogenesis. NBN gene mutations cause increased tumor risk in Nijmegen breakage syndrome (NBS) homozygotes as well as in NBN heterozygotes. NBS patients develop different types of malignancies; among solid tumors, medulloblastoma (MB), an embryonal tumor of the cerebellum, has been reported most frequently. The majority of medulloblastomas occur sporadically, some of them manifest within familial cancer syndromes. Several signaling pathways are known to be engaged in hereditary and sporadic MB. The aim of our study was to identify mutations in selected exons of the NBN gene and to determine the frequency of the most common NBN gene mutations in pediatric patients with different types of medulloblastoma. We screened a total of 104 patients with MB and identified 7 heterozygous carriers (6.7%) of two different germ-line mutations of NBN gene; all of them had classic MB. Our results indicate that heterozygous carriers of the germ-line NBN gene mutations (c.511A>G and c.657_661del5) may exhibit increased susceptibility to developing MB. The risk of medulloblastoma is estimated to be 3.0 (for c.511A>G) and 4.86 (for c.657_661del5) times higher than in the general Polish population (p<0.05). These results suggest that heterozygous NBN germ-line mutations may contribute to the etiology of medulloblastoma.

Long-term functional treatment outcome of cerebellar JPA is relatively favorable, in spite of permanent neurological deficits and emotional disorders in over half of the patients. Vermian tumors are associated with worse long-term functional outcome. Neurological deficits and emotional disorders do not preclude further education and independent functioning.

Six children with intraventricular tumors associated with tuberous sclerosis (TS) were treated at the Children's Health Center, Department of Pediatric Neurosurgery, in the period 1987-1992. The age of the patients ranged from 7 to 15 years. TS was diagnosed according to Gomez diagnostic criteria. Computer tomography (CT) and magnetic resonance imaging showed intraventricular tumors associated with ventricular enlargement and multiple subependymal nodules commonly observed in cases of TS. All tumors were removed totally through frontal transcortical approach, with uneventful postoperative recovery. One patient, with two parallel tumors in the two frontal horns, underwent one-stage surgery with successful total removal. Histopathological examination in all cases showed subependymal giant cell astrocytoma (SGCA). The growth pattern of SGCA associated with TS, documented by sequential CT scans over several years, is described. The diagnosis and surgical treatment of the tumor are discussed, and periodic CT scanning, at least every 2 years, is recommended for patients with TS.

An 8‐year‐old girl with severe microcephaly of prenatal onset, borderline intelligence, defects of skin pigmentation, deficiency of both humoral and cellular immunity, a normal serum α‐fetoprotein level and hypersensitivity to ionizing irradiation is described. Spontaneous chromosomal breakage in lymphocytes together with the clinical presentation led to the diagnosis of ataxia telangiectasia variant (AT‐V). In addition, the patient carried a constitutional translocation of paternal origin: 46,XX,t(3;7)(q12;q31.3) pat. In subsequent linkage and haplotype studies in 12 AT‐V families with microsatellite markers from each of the translocation breakpoint regions, we could clearly exclude the localization of an AT‐V gene to these regions.

To evaluate the risk factors for recurrence of MB/PNET we analyzed the medical records of 157 patients treated at the Children's Memorial Health Institute between February 1981 and February 1997. The following factors were evaluated: age at diagnosis, gender, tumor size, tumor cells in the CSF, postoperative status, extent of resection and methods of treatment. We evaluated chemotherapy (CHT) doses, interval between courses, interval between surgery (S) and first course of CHT, interval between S and radiotherapy (RTX), and breaks during RTX. We divided patients into six groups: S alone, S+CHT, S+RTX, S+CHT+ RTX, S+RTX+CHT, S+CHT+RTX+ CHT. Age at diagnosis, gender, tumor size, extent of resection, postoperative status, intervals between courses of CHT, between S and the first course of CHT, and between S and RTX, and breaks during RTX had no statistical influence on relapse occurrence. Tumor cells in CSF were routinely checked for from January 1992 onward. In this group of 75 patients, 40 had tumor cells positive at surgery (28 relapsed), while in the group of 35 patients with negative tumor cells 14 relapsed (P=0.004). Out of 26 patients treated with S+RTX alone, 13 relapsed. Among 14 patients treated with S+RTX and prolonged CHT 6 relapsed. Out of 14 patients treated with S+CHT 13 relapsed; among 49 who received S+CHT+RTX 35 relapsed; and out of 51 patients treated with S+CHT+RTX+CHT 30 relapsed. In the multivariate analysis of treatment methods chemotherapy implemented after radiotherapy had a positive, though not statistically significant, influence on outcome (P=0.06). Among those receiving CHT the mean percentage of the ideal dose administered had a statistically significant influence on relapse: in the group of relapsed patients the mean dose was 76.1%, while in the group in continuous remission it was 83.7% (P=0.0013). On the basis of our data, we conclude that the presence of tumor cells in the CSF had a significant influence on the occurrence of relapse. Administration of appropriate doses of chemotherapy is extremely important for the occurrence of relapse and the final outcome of treatment. Prolonged adjuvant chemotherapy after radiotherapy seems to lower the risk of recurrence.