Molecular genetics of pineal region neoplasms

Long Survival of Primary Pineal Melanoma with Radiation Treatment Only

Pineal gland tumors in adults account for about 0.4 to 1 % of all intracranial tumors. A wide variety of tumors can occur in the pineal gland. The most common are the pineal parenchymal tumors (pineocytomas, pineoblastomas, and pineal parenchymal tumors of intermediate differentiation), germ cell tumors, and glial tumors. Uncommonly in the pineal gland one may encounter a metastatic tumor, a meningioma or a melanoma.

We here report a case of primary pineal gland melanoma with prolonged survival of 56 weeks after radiotherapy alone. To our knowledge, this is the first reported case of prolonged survival after radiotherapy alone, without surgical intervention or chemotherapy. Contrary to previous reports, our case demonstrates that a pineal melanoma with leptomeningeal dissemination can still yield a better survival with radiation treatment only.

Is CRX protein a useful marker in differential diagnosis of tumors of the pineal region?

The cone-rod homeobox (CRX) is a gene that belongs to the member of the orthodenticle homeobox (Otx) family, with important function in development and differentiation of retinal and pineal cells. Moreover, CRX appears to be specifically expressed in pineal tumors and retinoblastomas. We performed an immunohistochemical study on 91 pediatric and adult central nervous system tumors, plus 2 normal brain samples. Our results demonstrated that CRX is expressed not only in pineal parenchymal tumors and retinoblastoma, but also in a some medulloblastomas and supratentorial primitive neuroectodermal tumors. None of the glial tumors screened were positive for CRX. In conclusion, CRX could be useful in surgical neuropathology for the differential diagnosis of pineal region tumors, in particular to discriminate pineal tumors from glial tumors.

Histopathology of tumors of the pineal region

Pineal region tumors are heterogeneous lesions and include mainly pineal parenchymal tumors (PPTs), papillary tumors of the pineal region (PTPRs) and germ cell tumors (GCTs). This article describes the cystic pineal gland compared with normal tissue and histopathological features of the most frequent pineal region tumors. PPTs are subdivided into pineocytoma (grade I), pineoblastoma (grade IV) and tumors with intermediate differentiation (PPTIDs; grades II-III). A grading system based on the number of mitoses and neurofilament protein expression distinguishes low- from high-grade PPTID. PTPR is a new tumoral entity thought to originate from the subcommissural organ. GCTs include germinoma, embryonal carcinoma, teratoma, yolk sac tumor and choriocarcinoma and are often of mixed histologic composition. New histogenetic data for GCTs are presented.

Current concepts in the molecular genetics of pediatric brain tumors: implications for emerging therapies

BACKGROUND

The revolution in molecular biology that has taken place over the past 2 decades has provided researchers with new and powerful tools for detailed study of the molecular mechanisms giving rise to the spectrum of pediatric brain tumors. Application of these tools has greatly advanced our understanding of the molecular pathogenesis of these lesions.

REVIEW

After familiarizing readers with some promising new techniques in the field of oncogenomics, this review will present the current state of knowledge as it pertains to the molecular biology of pediatric brain neoplasms. Along the way, we hope to highlight specific instances where the detailed mechanistic knowledge acquired thus far may be exploited for therapeutic advantage.

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

Classic cytogenetics has evolved from black and white to technicolor images of chromosomes as a result of advances in fluorescence in situ hybridization (FISH) techniques, and is now called molecular cytogenetics. Improvements in the quality and diversity of probes suitable for FISH, coupled with advances in computerized image analysis, now permit the genome or tissue of interest to be analyzed in detail on a glass slide. It is evident that the growing list of options for cytogenetic analysis has improved the understanding of chromosomal changes in disease initiation, progression, and response to treatment. The contributions of classic and molecular cytogenetics to the study of brain tumors have provided scientists and clinicians alike with new avenues for investigation. In this review the authors summarize the contributions of molecular cytogenetics to the study of brain tumors, encompassing the findings of classic cytogenetics, interphase- and metaphase-based FISH studies, spectral karyotyping, and metaphase- and array-based comparative genomic hybridization. In addition, this review also details the role of molecular cytogenetic techniques in other aspects of understanding the pathogenesis of brain tumors, including xenograft, cancer stem cell, and telomere length studies.

Advanced cancer genetics in neurosurgical research

RAPID ADVANCES IN the technology used to study nucleic acids have revealed a great deal regarding the underlying biology of cancer. Most cancers arise as a result of chromosomal rearrangements and deoxyribonucleic acid mutations that lead to the activation of proto-oncogenes and loss of function of tumor suppressor genes. There are a number of different molecular routes that lead to these common goals, necessitating several different techniques of mutational analysis. Although many of these techniques can be difficult in practice, most are conceptually simple. We discuss several of the current techniques in cytogenetics and molecular genetics that are widely used in cancer biology laboratories. Understanding the molecular events that lead to cancer should allow the future development of targeted, nontoxic therapeutics similar to modern-day antibiotics. These technologies are being progressively applied in clinical neurosurgery, where they will be used to detect, diagnose, stratify, and treat cancers of the nervous system. High demand from an increasingly educated patient population means that neurosurgeons will need to be familiar with many of these techniques.

Classifying the medulloblastoma: insights from morphology and molecular genetics

Significant advances in the treatment of the medulloblastoma (MB) have been made in the last 30 years, reducing mortality by 2-fold. Further improvements in the cure rate require an increased understanding of the biology of MBs, and this will translate into refinements in their classification. Scrutiny of the cytological variation found among MBs has recently led to the concept of the anaplastic MB, which overlaps the large-cell variant and appears to share its poor prognosis. In contrast, the MB with extensive nodularity, a distinctive nodular/desmoplastic variant occurring in infants, has a better outcome than most MBs in these young patients. Building on cytogenetic studies that have drawn attention to abnormalities on chromosome 17 in over a third of MBs, research shows non-random losses on chromosomes 8, 9, 10, 11 and 16, and gains on chromosomes 1, 7 and 9. Overexpression of ErbB2 receptors and losses on chromosome 17p have been proposed as independent indicators of aggressive behaviour, while high TrkC receptor expression indicates a favourable outcome. There is a strong association between anaplastic/large-cell tumours and MYC amplification, which has previously been linked with aggressive disease, but associations between abnormalities on chromosome 17 and anaplastic/large-cell MBs and between abnormalities in the shh/PTCH pathway and the desmoplastic variant are more controversial. Classification of the MB histopathologically and according to profiles of molecular abnormalities will help both to rationalize approaches to therapy, increasing the cure rate and reducing long-term side-effects, and to suggest novel treatments.