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Are Juvenile Pilocytic Astrocytomas Benign Tumors? A Cytogenetic Study in 24 Cases

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Abstract

We performed a cytogenetic study on 24 pilocytic astrocytomas: 23 in children and 1 in a young adult. We observed 12 normal karyotypes. In 12 karyotypes with structural and/or numerical abnormalities, chromosomes 7, 8, and 11 were most frequently involved. One case recurred and presented chromosomal abnormalities (hyperdiploidy) in the first tumor and additional structural abnormalities in the second tumor. We believe that chromosomal abnormalities in pilocytic astrocytomas are frequent and indicate tumoral progression.

Introduction

Juvenile pilocytic astrocytomas are central nervous system tumors that usually occur in children or adolescents. They differ clinically, histopathologically, and cytogenetically from astrocytomas that affect adults. Juvenile pilocytic astrocytomas are predominantly low grade tumors. The most common sites of these tumors are the cerebellum and the thalamus; usually the prognosis is excellent, with survival rates approaching 100% [1].

There have been some cytogenetic studies of these tumors 2, 3, 4, 5, 6, 7, 8, 9. In general, the karyotypes of low-grade astrocytomas (grade I, grade II, or pilocytic tumors) are normal 2, 7, 8, 10, 11. Adult astrocytomas have revealed allelic losses on chromosomes 10, 17p, and 19q and alterations in the epidermal growth factor receptor (EGFR) gene 12, 13, 14, 15. Cytogenetic studies have noted that, when compared with lower grade tumors, higher grade astrocytomas and glioblastomas tend to be characterized by an increasing complexity of chromosomal aberrations [16].

We report here the karyotypes realized in 24 cases of juvenile pilocytic astrocytomas. In our report, 12 cases show chromosomal abnormalities and one of them recurs as a glioblastoma.

Section snippets

Materials and methods

Tumor tissue was obtained from 24 patients (23 children and 1 young adult) who had undergone tumoral resection. The histopathologic diagnosis of all of these tumors was pilocytic astrocytoma.

Sterile tumor tissue was obtained from the operating room and immediately taken to the laboratory, where it was dissected by the use of aseptic techniques. First, tumor tissue was finely minced with a scalpel, and bloody and necrosed portions were discarded.

Next, the fragments were disaggregated in

Results

The pilocytic astrocytomas that we studied are listed in Table 1. In these tumors, we examined the sex and age of the patient, the site of tumor origin, and the karyotype. Briefly, the children’s age at presentation ranged from 1 to 14 years and the young adult was 19 years old. Tumor location was often the cerebellum. One patient carried a diagnosis of neurofibromatosis (case no. 22).

Cytogenetic study showed the existence of normal karyotypes in 12 cases. In the other tumors (12 cases), we

Discussion

We performed a cytogenetic study of 24 pilocytic astrocytomas: 23 in children and 1 in a young adult. Most authors have reported normal karyotypes in these tumors 2, 6, 8, 11. We observed only 12 normal karyotypes. In our study, clonal cytogenetic abnormalities (gains or structural abnormalities) most frequently involve chromosomes 7, 8, and 11. White et al. [9], relying on additional karyotypic data that have been published, performed fluorescence in situ hybridization with specific probes of

References (20)

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