Cytogenetic and histopathologic studies of congenital supratentorial primitive neuroectodermal tumors: a case report

Brain tumors in the first two years of life

Background

Brain tumors in the first years of life are frequently encountered recently with the advancement in neuroimaging, neurosurgery and neuroanethesia where early diagnosis of these lesions became available even before birth. Their management is challenging where the surgery is technically demanding, radiotherapy is omitted in this age because of its late sequelae and chemotherapy role may be beneficial, but it is limited also by its side effects and neurotoxicity. The aim of this article is to review the current literature about the brain tumors in the first two years of life, their diagnosis and treatment.

Main body

Brain tumors in the first two years of life encompass mainly fetal/congenital tumors and infantile tumors. They account for 1.4–18% of cases of pediatric brain tumor, and most of them are diagnosed in the first year of life. The main histopathologies diagnosed are glial tumors, choroid plexus tumors, medulloblastoma and other embryonal tumors, teratoma and ependymoma. They are mainly supratentorial. Large head and bulging fontanelles are the main presenting symptoms and signs secondary to increased intracranial pressure secondary to large tumors or associated hydrocephalus. Prenatal and postnatal ultrasonography represents the initial imaging step in the diagnosis that should be complemented by MRI and CT brain. The main and first line of treatment of infantile brain tumors is surgical excision as the prognosis is directly related to the extent of resection besides surgery offers specimens for histopathological diagnosis and adjuvant chemotherapy is given for residual irresectable cases and malignant tumors with the main aim to delay radiotherapy beyond the age of three years.

Conclusion

Brain tumors in the first two years of life are a challenging group of different histopathological entities with underlying specific molecular characterization and genetic predispositions. They have aggressive behavior and general poor prognosis with limited options of management. Individualized multidisciplinary management for each case is needed, and future studies for therapeutic medications targeting underlying molecular biology may improve their outcome.

Congenital tumors of the central nervous system

Congenital tumors of the central nervous system (CNS) are often arbitrarily divided into "definitely congenital" (present or producing symptoms at birth), "probably congenital" (present or producing symptoms within the first week of life), and "possibly congenital" (present or producing symptoms within the first 6 months of life). They represent less than 2% of all childhood brain tumors. The clinical features of newborns include an enlarged head circumference, associated hydrocephalus, and asymmetric skull growth. At birth, a large head or a tense fontanel is the presenting sign in up to 85% of patients. Neurological symptoms as initial symptoms are comparatively rare. The prenatal diagnosis of congenital CNS tumors, while based on ultrasonography, has significantly benefited from the introduction of prenatal magnetic resonance imaging studies. Teratomas constitute about one third to one half of these tumors and are the most common neonatal brain tumor. They are often immature because of primitive neural elements and, rarely, a component of mixed malignant germ cell tumors. Other tumors include astrocytomas, choroid plexus papilloma, primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumors, and medulloblastomas. Less common histologies include craniopharyngiomas and ependymomas. There is a strong predilection for supratentorial locations, different from tumors of infants and children. Differential diagnoses include spontaneous intracranial hemorrhage that can occur in the presence of coagulation factor deficiency or underlying vascular malformations, and congenital brain malformations, especially giant heterotopia. The prognosis for patients with congenital tumors is generally poor, usually because of the massive size of the tumor. However, tumors can be resected successfully if they are small and favorably located. The most favorable outcomes are achieved with choroid plexus tumors, where aggressive surgical treatment leads to disease-free survival.

A prenatal diagnosed case of primitive neuroectodermal tumor

Congenital brain tumors presenting in the first year of life account for 1.4-8.5% of all childhood brain tumors. Only 18% of congenital brain tumors are diagnosed before or at delivery. Primitive neuroectodermal tumor (PNET) is a highly malignant, small, blue-cell tumor which is characterized by early recurrence, metastasis, and high mortality. It makes up 13% of all fetal and neonatal brain tumors. Prenatal diagnosis of PNET or other congenital brain tumors is important because the presence of tumors may alter the time and mode of delivery and postnatal care planning. A prenatal case of PNET is described that was diagnosed with ultrasonography and magnetic resonance imaging; the case was confirmed histopathologically at postmortem examination.

Endoscopic biopsy interpretation difficulties in a congenital diffuse intracranial teratoma

INTRODUCTION

Congenital brain tumours are a rare entity that is nowadays often already recognised during pregnancy by ultrasound (US) and magnetic resonance (MR). Even though the definitive diagnosis is usually achieved by means of histological studies, in some cases the diagnosis may remain uncertain because of the malformative origin of this type of tumour.

CASE REPORT

We describe a patient with a diffuse congenital intracranial mass diagnosed by intrauterine US and foetal MR performed to further evaluate the lesion and the associated foetal hydrocephalus. After delivery by caesarean section, an endoscopic biopsy was performed. Several specimens were obtained and resulted in the diagnosis of primitive neuroectodermal tumour (PNET). Despite polychemotherapy, the tumour continued to enlarge and the patient died at 2 months of age. Post-mortem histological examination of the intracranial mass showed a diffuse intracranial teratoma.

CONCLUSION

Endoscopic biopsy specimen examination resulted in a diagnosis that was not confirmed by post-mortem findings. The scarce differentiation of teratoma components and their high variability in histomorphology as well as the huge size of the tumoral mass may limit the interpretation of endoscopic biopsy specimens, even when multiple and obtained from different areas.

Molecular genetics of supratentorial primitive neuroectodermal tumors and pineoblastoma

The supratentorial primitive neuroectodermal tumors (PNETs) are a group of highly malignant lesions primarily affecting young children. Although these tumors are histologically indistinguishable from infratentorial medulloblastoma, they often respond poorly to medulloblastoma-specific therapy. Indeed, existing molecular genetic studies indicate that supratentorial PNETs have transcriptional and cytogenetic profiles that are different from those of medullo-blastomas, thus pointing to unique biological derivation for the supratentorial PNET. Due to the rarity of these tumors and disagreement about their histopathological diagnoses, very little is known about the molecular characteristics of the supratentorial PNET. Clearly, future concerted efforts to characterize the molecular features of these rare tumors will be necessary for development of more effective supratentorial PNET treatment protocols and appropriate disease models. In this article the authors review existing molecular genetic data derived from human and mouse studies, with the aim of providing some insight into the putative histogenesis of these rare tumors and the underlying transforming pathways that drive their development. Studies of the related but distinct pineoblastoma PNET are also reviewed.

The epidemiology of neonatal tumours. Report of an international working group

Neonatal tumours occur every 12,500-27,500 live births and comprise 2% of childhood malignancies, but there is little clarity as to their real prevalence, sites of origin and pathological nature as reported series vary. As an entity, neonatal tumours provide a unique window of opportunity to study tumours in which minimal environmental interference has occurred. The majority of tumours present with a mass at birth (e.g., teratomas, neuroblastomas, mesoblastic nephroma, fibromatosis), which are not infrequently identified on antenatal ultrasound. Histologically, teratoma and neuroblastoma remain the two main tumour types encountered with soft tissue sarcoma, renal tumours, CNS tumours and leukaemia being the next most common tumour types identified. Malignant tumours are uncommon in the neonatal period per se and benign tumours may have malignant potential. A particular problem exists in clinical classification, as histological features of malignancy do not always correlate with clinical behaviour. Benign tumours may also be life threatening because of their size and location. Other tumours may demonstrate local invasiveness, but no metastatic potential, and tumours that are clearly malignant may demonstrate unpredictable or uncertain behaviour. Screening programmes have brought more tumours to light, but do not appear to affect the overall prognosis. They may provide clues to the stage at which tumours develop in foetu. The aetiology of cancer in children is multifactorial and includes both genetic and environmental factors. The association between congenital abnormalities and tumours is well established (15% of neonatal tumours). Genetic defects are highly likely in neonatal tumours and include those with a high risk of malignancy (e.g., retinoblastoma), but also genetically determined syndromes with an increased risk of malignancy and complex genetic rearrangements. Tumours are mostly genetically related at a cellular level and factors influencing cellular maturation or apoptosis within the developing foetus may continue to operate in the neonatal period. Cytogenetics of neonatal neoplasms appear to differ from neoplasms in older children, thus possibly explaining some of the observed differences in clinical behaviour. Certain constitutional chromosome anomalies, however, specifically favour tumours occurring in the foetal and neonatal period. In support of this hypothesis, certain cytogenetic anomalies appear to be specific to neonates, and a number of examples are explored. Other environmental associations include ionizing radiation, drugs taken during pregnancy, infections, tumours in the mother and environmental exposure.

Unusual aberration involving the short arm of chromosome 11 in an 8-month-old patient with a supratentorial primitive neuroectodermal tumor

An 8-month-old baby girl with a supratentorial primitive neuroectodermal tumor showed an unusual aberration involving the short arm of chromosome 11. Seven abnormal metaphase cells had 49 chromosomes with trisomies of chromosomes 9 and 13, and partial trisomies of 1q and 18p. One homologue chromosome 11 was strikingly abnormal showing a long acrocentric-like form, which was composed of the long arm of chromosome 1 and an addition to the short arm of chromosome 11. This was characterized by fluorescence in situ hybridization using a partial arm chromosome-painting probe.

I. Perinatal brain tumors: a review of 250 cases

Central nervous system tumors occur considerably less often in the fetus and neonate than in the older child. These tumors are not entirely the same as those found later in life. Their location, biologic behavior, response to therapy, and histologic types are different. Reports of 250 fetal and neonatal brain tumors were collected from the literature and studied for this review. The overall survival rate was 28%. The entire cranial cavity may be filled with tumor, and stillbirth is not uncommon. Macrocephaly was the most frequent presentation regardless of histology. Outcome is related to the size and location of the tumor, the histologic type, surgical resectability, and the condition of the infant at the time of diagnosis. Neonates with choroid plexus papillomas, gangliogliomas, and low-grade astrocytomas have the best prognosis, whereas those with teratomas and primitive neuroectodermal tumors have the worst prognosis.

Primitive neuroectodermal tumors/medulloblastoma

The therapy for medulloblastoma/primitive neuroectodermal tumors of the central nervous system is surgery, followed by combination chemo-radiotherapy. The radiation field is the entire craniospinal axis, which is only avoided when treating infants. The treatment is, therefore, lengthy and toxic. Less aggressive therapy is given to patients who clinically appear to have less evidence of disease. Intensive basic research has begun to identify genetic factors of the disease, but these remain far from clinical application.