Oligodendroglioma occurring after radiation therapy for pituitary adenoma

Hypothalamic Endocrine Tumors: An Update

The hypothalamus is the site of synthesis and secretion of a number of endocrine peptides that are involved in the regulation of hormonal activity of the pituitary and other endocrine targets. Tumors of the hypothalamus have been recognized to have both structural and functional effects including hormone hypersecretion. The classification of these tumors has advanced over the last few years, and biomarkers are now available to classify these tumors and provide accurate structure-function correlations. This review provides an overview of tumors in this region that is critical to metabolic homeostasis with a focus on advances in the diagnosis of gangliocytomas, neurocytomas, and pituicytomas that are unique to this region.

Secondary Intracranial Tumors Following Radiotherapy for Pituitary Adenomas: A Systematic Review

Pituitary adenomas are often treated with radiotherapy for the management of tumor progression or recurrence. Despite the improvement in cure rates, patients treated by radiotherapy are at risk of development of secondary malignancies. We conducted a comprehensive literature review of the secondary intracranial tumors that occurred following radiotherapy to pituitary adenomas to obtain clinicopathological characteristics. The analysis included 48 neuroepithelial tumors, 37 meningiomas, and 52 sarcomas which were published between 1959–2017, although data is missing regarding overall survival and type of irradiation in a significant proportion of the reports. The average onset age for the pituitary adenoma was 37.2 ± 14.4 years and the average latency period before the diagnosis of the secondary tumor was 15.2 ± 8.7 years. Radiotherapy was administered in pituitary adenomas at an average dose of 52.0 ± 19.5 Gy. The distribution of pituitary adenomas according to their function was prolactinoma in 10 (7.2%) cases, acromegaly in 37 (27.0%) cases, Cushing disease in 4 (2.9%) cases, PRL+GH in 1 (0.7%) case, non-functioning adenoma in 57 (41.6%) cases. Irradiation technique delivered was lateral opposing field in 23 (16.7%) cases, 3 or 4 field technique in 27 (19.6%) cases, rotation technique in 10 (7.2%) cases, radio surgery in 6 (4.3%) cases. Most of the glioma or sarcoma had been generated after lateral opposing field or 3/4 field technique. Fibrosarcomas were predominant before 1979 (p < 0.0001). The median overall survival time for all neuroepithelial tumors was 11 months (95% confidence intervals (CI), 3–14). Patients with gliomas treated with radiotherapy exhibited a non-significant positive trend with longer overall survival. The median overall survival time for sarcoma cases was 6 months (95% CI, 1.5–9). The median survival time in patients with radiation and/or chemotherapy for sarcomas exhibited a non-significant positive trend with longer overall survival. In patients treated with radiotherapy for pituitary adenomas, the risk of secondary tumor incidence warrants a longer follow up period. Moreover, radiation and/or chemotherapy should be considered in cases of secondary glioma or sarcoma following radiotherapy to the pituitary adenomas.

A case of multiple radiation-induced gliomas 24 years after radiation therapy against pituitary adenoma

We treated a case in which multiple astrocytomas of varying grades developed in the irradiation field 24 years after radiation therapy. Differentiation from radiation necrosis based on presurgical diagnostic imaging was difficult; therefore, we feel it is essential to aggressively pursue histological diagnoses to select the optimal treatment method.

Secondary oligodendroglioma after postoperative irradiation for medulloblastoma: a case report and review of the literature

Medulloblastoma, a malignant, invasive embryonal tumor of the cerebellum, occurs most often in children. It has high metastatic potential and is usually treated by aggressive multimodal therapy, including surgery, chemotherapy and craniospinal irradiation. Multiple secondary tumors have been reported following craniospinal irradiation. It is rare with the occurrence of oligodendroglioma after irradiation. In this report, we described a patient with secondary oligodendroglioma after postoperative craniospinal irradiation for medulloblastoma.

Loss of heterozygosity analysis in an anaplastic oligodendroglioma arising after radiation therapy

OBJECTIVE AND IMPORTANCE

Oligodendroglial tumors rarely occur after radiation therapy. Here, we report a rare case of anaplastic oligodendroglioma arising after radiation therapy, in which genetic analysis was performed.

CLINICAL PRESENTATION AND INTERVENTION

A 41-year-old man who had received radiation therapy for a tumor of the suprasellar and pineal regions 31 years previously, presented with headache and progressive right hemiparesis. Magnetic resonance (MR) images revealed a ring-enhanced mass lesion in the left frontal lobe. Total removal of the tumor was performed through left frontoparietal craniotomy, and the histologic diagnosis was anaplastic oligodendroglioma. Using 23 microsatellite markers, the allelic status of chromosomes 1p, 10, 17p and 19q was evaluated by a PCR-based loss of heterozygosity (LOH) assay. Markers on chromosomes 1p, 17p and 19q revealed LOH, but none of the markers on chromosome 10 showed LOH. Based on the genetic analysis, this tumor was considered to be sensitive to chemotherapy. Two courses of chemotherapy, with procarbazine, ACNU and vincristine, were performed. However, tumor recurrence was detected only 3 months after the surgery. Despite additional radiochemotherapy, the tumor aggressively increased in size and the patient died with multiple recurrent tumors 1 year after surgery.

CONCLUSION

The anaplastic oligodendroglioma presented in this report showed a more aggressive clinical course than was expected from the genetic analysis. The significance of 1p and 19q LOH in radiation-induced oligodendroglial tumors might differ from that in spontaneous counterparts.

Intracranial malignancies occurring more than 20 years after radiation therapy for pituitary adenoma

A 37-year-old woman developed a left third cranial nerve palsy 28 years after radiation for a nonsecreting pituitary adenoma. Imaging disclosed a left parasellar mass and a midbrain/pontine signal abnormality. Biopsy of the parasellar mass revealed a malignant sarcoma. The brainstem abnormality was presumptively diagnosed as a malignant glioma. A 63-year-old man developed a malignant astrocytoma of the left optic nerve and chiasm 23 years after partial excision and radiation of a nonsecreting pituitary adenoma. Both patients died of their malignancies. Although secondary malignancies have been described in this setting, such long latencies have not been reported.

Anaplastic oligodendrogliomas after treatment of acute lymphoblastic leukemia in children: report of 2 cases

Radiation-induced brain tumors are suggested to be the late complication of acute lymphoblastic leukemia (ALL) treatment. High-grade gliomas, meningiomas, and sarcomas are the most frequent neoplasms. Secondary anaplastic oligodendrogliomas are exceedingly rare. Five cases of pure anaplastic oligodendroglioma have been reported in the literature, and only 1 case was in a child after ALL treatment. The authors present 2 cases of pediatric anaplastic oligodendroglioma after treatment of ALL. Furthermore, they performed a molecular cytogenetic study and found loss of 1p in both cases. The authors provide a review of the previous cases and discuss their findings.

Radiation-induced gliomas following radiotherapy for craniopharyngiomas: a case report and review of the literature

The aim of this study was to collect, describe and analyze the radiation-induced gliomas in craniopharyngioma patients reported in the literature up to date. Review of the relevant literature was performed. One personal illustrative case was added. Reports of 15 patients, including the presented illustrative case, were evaluated. The average age of the patients at the time of irradiation was 12.5 years. All patients underwent conventional fractionated radiotherapy with mean total radiation dose of 55Gy and an average latency period of 10.8 years. Glioma localization varied with the highest frequency of the temporal lobe involvement. All but one patient had high-grade gliomas on the histological exam. Although exceptionally rare, the radiation-induced gliomas in craniopharyngioma patients are potentially possible, long-term complications with devastating consequences in typically younger patients with long life-expectancy. The radiation-induced iatrogenic injury on one hand should provoke the research and elaboration of safer and at least, equally efficient alternative treatment modalities and on the other hand ought to prompt the investigation of the patients' risk factors predisposing the oncogenesis after irradiation.

Molecular pathology of oligodendroglial tumors

The term oligodendroglioma was created by Bailey, Cushing, and Bucy based on the observation that these tumors share morphological similarities with oligodendrocytes (Bailey and Cushing 1926; Bailey and Bucy 1929). However, a convincing link between oligodendrocytes and oligodendrogliomas still needs to be shown. Oligoastrocytomas or mixed gliomas are histologically defined by the presence of oligodendroglial and astrocytic components. According to the WHO classification of brain tumors, oligodendroglial tumors are separated into oligodendrogliomas WHO grade II (OII), anaplastic oligodendrogliomas WHO grade III (OIII), oligoastrocytomas WHO grade II (OAII), anaplastic oligoastrocytomas WHO grade III (OAIII), and glioblastomas with oligodendroglioma component WHO grade IV (GBMo) (Louis et al. 2007).The perception of oligodendroglial tumors has changed in recent years. The diagnosis of oligodendroglioma or oligoastrocytomas is made much more frequently than 10 years ago. Treatment modalities have been advanced and novel concepts regarding the origin of oligodendroglial tumors have been developed. This review focuses on recent developments with impact on the diagnosis and understanding of molecular mechanisms in oligodendroglial tumors.

Surgical removal of small petroclival meningiomas

Treatment of large petroclival meningiomas causing brain stem compression is surgical removal followed by radiotherapy or radiosurgery if the lesion was partially resected. The management of small petroclival meningiomas is, however, controversial. Clinical observation, radiosurgery and surgical removal are the options of treatment. The natural history of these tumours is not well known. Published series of patients treated with radiosurgery are not comparable with surgical series because the latter also includes large size tumours. In this paper we present a series of 18 patients with small petroclival meningiomas (diameter <or= 2.8 cm) treated with radical surgical removal. Total resection (Simpson's Grade 1) [43] was possible with minimal morbidity and no mortality.

BACKGROUND

We present a series of small petroclival meningiomas (SPM) treated by radical surgical removal and compare the outcome with other management modalities proposed for these lesions.

METHODS

Eighteen patients with SPM were surgically treated at our department of neurological surgery. The tumours were classified as small when they had a diameter < 3.0 cm. Headaches (n = 12), diplopia (n = 8), facial hypoaesthesia (n = 3) and tinnitus (n = 6) were the most frequent symptoms at presentation. The approaches used were retrosigmoid (n = 14), fronto-orbito-zygomatic (n = 3) and presigmoid (n = 1). The post-operative follow-up ranged from 1 to 110 months (mean 41.8 months).

FINDINGS

Radical tumour resection (Simpson's Grades 1 and 2) was achieved in all patients. There was no major morbidity or mortality related to the surgical procedure. Transient abducent nerve palsy was the only post-operative complication. The pre-operative cranial nerves deficits improved after surgery. Only one patient had persistent diplopia postoperatively.

CONCLUSION

Radical surgical removal of SPM is possible with minimal morbidity and may cure the patient. The effectiveness and outcome of surgery for small petroclival meningiomas should be compared with series treated by radiosurgery.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO ‘Blue Book’, the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

The 2007 WHO classification of tumours of the central nervous system

The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.

Oligodendroglioma of the pineal region

✓ The authors describe an oligodendroglioma of the pineal region in a 59-year-old woman. The patient presented with intermittent confusion, memory disturbance, and headache associated with a cystic pineal region mass demonstrated on magnetic resonance imaging. Gross-total resection was performed via a suboccipital supratentorial approach. Pathological and genetic evaluation showed the tumor to be an anaplastic oligodendroglioma. Although the spectrum of tumors arising within the region of the pineal gland is broad, to the authors’ knowledge this is the first report of an oligodendroglioma occurring in this area.

The Burden of Radiation-Induced Central Nervous System Tumors

Radiation-induced tumors of the central and peripheral nervous systems are becoming a noticeable subset of tumors seen at referral institutions. This paper outlines a single institution s experience with 22 examples of secondary meningiomas, gliomas, and sarcomas that developed in adults. These tumors are being increasingly encountered by physicians, but the greatest burden is on the patients themselves, who not only experience the life-altering effects of the original tumor and the subsequent delayed cognitive effects of radiotherapy, but later develop a second intracranial neoplasm. We detail a particularly poignant example of a 34-year-old man who developed a high-grade sarcoma with rhabdomyosarcomatous and osteogenic elements. Local control was difficult over the next year, and he eventually developed cerebrospinal fluid dissemination and succumbed. Although radiation-induced neoplasm remain relatively infrequent numerically, each case reminds us of the need for new, less toxic, and more targeted therapies for brain neoplasms.

Pathology and molecular genetics of oligodendroglial tumors

Oligodendroglial gliomas are second only to astrocytic gliomas in frequency. The lack of stringent diagnostic criteria cause high interobserver variation in regard to classification and grading of these tumors. Previous studies have described oligodendrogliomas with features that overlap with those of neurocytic tumors, thus further complicating diagnostic decisions. The increasing need for standardized diagnostic criteria in this subset of gliomas is emphasized by the benefit of adjuvant therapies in patients with anaplastic oligodendrogliomas. Characteristic chromosomal aberrations have been successfully determined for oligodendroglial tumors in recent years. In contrast to astrocytomas, however, no genes in the affected regions have been clearly linked to their pathogenesis. However, the molecular findings promise to be helpful for diagnostic and therapeutic decisions. This review compiles clinical, pathological, and molecular genetic findings on WHO grades II and III oligodendrogliomas and oligoastrocytomas.

Malignant transformation of a dysembryoplastic neuroepithelial tumor after radiation and chemotherapy

We describe a case of anaplastic astrocytoma in a 14-year-old boy arising at the site of a dysembryoplastic neuroepithelial tumor (DNT) 3 years after combined radiation and chemotherapy. The subtotally excised superficial right temporoparietal tumor was originally diagnosed as mixed oligoastrocytoma in 1974; the patient was treated with radiation therapy postoperatively. One year later he underwent a craniotomy to remove cyst fluid and no change was reported in the size of the residual tumor. Postoperatively, he received a 6-week course of chemotherapy (lovustine, CCNU). He remained clinically and radiographically stable until 3 years later, when seizure activity returned and imaging studies were consistent with tumor recurrence. He was lost to follow-up until 1986, when records showed that he had died. Review of the initial biopsy showed cortical fragments containing abundant calcifications and multinodular structures typical of the complex form of DNT, in addition to specific glioneuronal elements. The Ki-67 labeling index ranged from 0.1% to 3% focally. The specimen from the third surgery showed an anaplastic astrocytoma (Ki-67 up to 12%) and morphologic features characteristic of radiation effect. This is the first documented case of malignant transformation of DNT following radiation and adjuvant chemotherapy. The implications of malignant transformation in subtotally excised complex DNTs and the intriguing issue of the contribution of radiation/chemotherapy are discussed.

Gamma knife radiosurgery and its possible relationship to malignancy: a review

✓ The question has been raised recently whether gamma knife radiosurgery (GKS) can induce secondary neoplasia. Because there is little or no detailed knowledge about this potential complication, background information culled from the radiotherapy literature is reviewed as a guide to the clinical situations in which radiotherapy may induce secondary neoplastic change. Available case reports are then reviewed and discussed against the background of the current knowledge. On the basis of the review, the following suggestions are proposed on how to limiting the extent of this complication, document its frequency, and inform patients. It should be remembered that: the benefits of GKS are great; its alternatives also have risks; there often are no alternatives to GKS; follow-up documentation should be pursued more actively so that, if possible, no patient falls through the net; practitioners should be proactive in defining the problem, and genetic analysis of tumor biopsy specimens obtained in patients who will undergo or have undergone GKS should become routine; the extent of secondary neoplasia is not known; and patient information should be guided by what is known rather than by what is feared.

Glioma occurrence after sellar irradiation: case report and review

OBJECTIVE

Tumor neogenesis is an uncommon but known consequence after therapeutic irradiation of the central nervous system. Causative agents for glioma induction remain unknown, but laboratory and clinical data suggest a possible role for radiation as a promotor. In the treatment of both pituitary adenomas and craniopharyngiomas, adjunctive conventional radiation therapy has long played a role.

CLINICAL PRESENTATION

This report details two cases in which patients received standard sellar irradiation for growth hormone-secreting pituitary adenomas and later were diagnosed with gliomas, after a latency period of 11 and 18 years, respectively. Additionally, a comprehensive review of the literature with 30 reports of gliomas developing after conventional radiation for treatment of pituitary adenomas and craniopharyngiomas is presented. The mean dose for craniopharyngiomas (n = 8) was 5800 cGy, with a mean latency of 11.5 years from initial diagnosis to the eventual discovery of the gliomas. The mean dose for the treatment of pituitary adenomas (n = 24) was 5300 cGy, with a mean latency of 10.4 years.

CONCLUSION

Typical features of the resulting gliomas included presentation in young patients, histologically high grades, and occurrence within the temporal lobe. A large proportion of gliomas were associated with growth hormone-secreting adenomas. This review assesses the implication of doses of conventional radiotherapy that were previously thought to be benign and concludes that although radiation-associated gliomas are uncommon, they represent a potentially devastating long-term risk. Based on this analysis, treatment of sellar tumors with conventional fractionated radiotherapy should be carefully considered and perhaps used primarily in those cases for which radiosurgery is not appropriate.

Homozygous p53 gene mutation in a radiation-induced glioblastoma 10 years after treatment for an intracranial germ cell tumor: case report

OBJECTIVE

Radiation-induced glioma is a rare but serious complication of radiotherapy. Underlying radiation-induced mutations in oncogenes or tumor suppressor genes have not previously been described.

CLINICAL PRESENTATION

A 16-year-old female patient developed a glioblastoma in the right frontal lobe 10 years after treatment of a suprasellar germ cell tumor with 50 Gy ionizing radiation. The glioblastoma was undetectable on a high-resolution magnetic resonance image obtained 3 months before diagnosis.

METHODS AND RESULTS

A p53 functional assay was used to examine the transcriptional competence of the p53 tumor suppressor gene. This assay scores the content of mutant p53 alleles in tumor and blood samples quantitatively as a percentage of red yeast colonies. The glioblastoma contained 95% mutant p53 alleles, whereas blood from the patient and her parents contained only normal background levels of red colonies. Sequencing revealed that the mutation in the tumor was a 3-base pair deletion affecting codons 238 and 239. Intragenic deletion within the p53 deoxyribonucleic acid binding domain is uncommon in sporadic tumors but would be entirely consistent with misrepair of a radiation-induced double-strand deoxyribonucleic acid break in this case.

CONCLUSION

This is the first case in which a causative underlying genetic event has been identified in a radiation-induced glioblastoma. We infer that mutation of one p53 allele occurred at the time of radiotherapy, and the sudden appearance of the tumor 10 years later occurred after loss of the remaining wild-type allele and/or other genetic alterations, such as chromosome 10 loss and epidermal growth factor receptor gene amplification.