Pathology of tumors of the pineal region

Pineal/germ cell tumors and pineal parenchymal tumors

INTRODUCTION

Pineal region tumors (PRTs) are tumors arising from the pineal gland and the paraspinal structures. These tumors are rare and heterogeneous that account for 2.8-10.1% and 0.6-3.2% of tumors in children and in all ages, respectively. Almost all types and subtypes of CNS tumors may be diagnosed in this region. These tumors come from cells of the pineal gland (pinealocytes and neuroglial cells), ectopic primordial germ cells (PGC), and cells from adjacent structures. Hence, PRTs are consisted of pineal parenchyma tumors (PPTs), germ cell tumors (GCTs), neuroepithelial tumors (NETs), other miscellaneous types of tumors, cystic tumors (epidermoid, dermoid), and pineal cyst in addition. The symptoms of PRTs correlate to the increased intracranial cranial pressure due to obstructive hydrocephalus and dorsal midbrain compression. The diagnostic imaging studies are mainly MRI of brain (with and without gadolinium) along with a sagittal view of whole spine. Serum and/or CSF AFP/β-HCG helps to identify GCTs. The treatment of PRTs is consisted of the selection of surgical biopsy/resection, handling of hydrocephalus, neoadjuvant and/or adjuvant therapy according to age, tumor location, histopathological/molecular classification, grading of tumors, staging, and threshold value of markers (for GCTs) in addition.

METHODS

In this article, we review the following focus points: 1. Background of pineal region tumors. 2. Pineal GCTs and evolution of management. 3. Molecular study for GCTs and pineal parenchymal tumors. 4. Review of surgical approaches to the pineal region. 5. Contribution of endoscopy. 6. Adjuvant therapy (chemotherapy, radiotherapy, and combination). 7.

FUTURE DIRECTION

RESULTS

In all ages, the leading three types of PRTs in western countries were PPTs (22.7-34.8%), GCTs (27.3-34.4%), and NETs (17.2-28%). In children and young adults, the leading PRTs were invariably in the order of GCTs (40-80.5%), PPTs (7.6-21.6%), NETs (2.4-37.5%). Surgical biopsy/resection of PRTs is important for precision diagnosis and therapy. Safe resection with acceptable low mortality and morbidity was achieved after 1970s because of the advancement of surgical approaches, CSF shunt and valve system, microscopic and endoscopic surgery. Following histopathological diagnosis and classification of types and subtypes of PRTs, in PPTs, through molecular profiling, four molecular groups of pineoblastoma (PB) and their oncogenic driver were identified. Hence, molecular stratified precision therapy can be achieved.

CONCLUSION

Modern endoscopic and microsurgical approaches help to achieve precise histopathological diagnosis and molecular classification of different types and subtypes of pineal region tumors for risk-stratified optimal, effective, and protective therapy. In the future, molecular analysis of biospecimen (CSF and blood) along with AI radiomics on tumor imaging integrating clinical and bioinformation may help for personalized and risk-stratified management of patients with pineal region tumors.

Accuracy of apparent diffusion coefficient values for distinguishing between pineal germ cell tumour and pineoblastoma

AIM

To differentiate between pineal germ cell tumour and pineoblastoma using apparent diffusion coefficient (ADC) values due to their overlapping imaging findings on magnetic resonance imaging (MRI).

MATERIALS AND METHODS

This retrospective study was conducted on 33 patients with pineal germ cell tumours and eight patients with pineoblastoma who underwent pretreatment MRI. Twenty-seven patients (21 with pineal germ cell tumour and six with pineoblastoma) were included for ADC measurement. The minimum and mean ADC values of the tumours were measured, with normalized tumour to control ADC ratios generated. The MRI characteristics of the tumours were evaluated.

RESULTS

The mean and minimum ADC values, normalized mean and minimum ADC ratios of pineal germ cell tumours were significantly higher than those of pineoblastomas (all p<0.005). A cut-off value of 0.92 for the normalized mean ADC ratio was used to distinguish between pineal germ cell tumour and pineoblastoma and achieved an area under the curve of 0.95, sensitivity of 90.5%, specificity of 83.3%, and accuracy of 92.6%. An equal degree of contrast enhancement to the adjacent venous sinus was the only MRI characteristic that suggested the diagnosis of pineal germ cell tumour.

CONCLUSION

The ADC values could help differentiate between pineal germ cell tumour and pineoblastoma, specifically when conventional MRI findings are indeterminate.

Rosette-Forming Glioneuronal Tumor in the Pineal Region: A Series of 6 Cases and Literature Review

Resected lesions from the pineal region are rare specimens encountered by surgical pathologists, and their heterogeneity can pose significant diagnostic challenges. Here, we reviewed 221 pineal region lesions resected at New York-Presbyterian Hospital/Columbia University Irving Medical Center from 1994 to 2019 and found the most common entities to be pineal parenchymal tumors (25.3%), glial neoplasms (18.6%), and germ cell tumors (17.6%) in this predominantly adult cohort of patients. Six cases of a rare midline entity usually found exclusively in the fourth ventricle, the rosette-forming glioneuronal tumor, were identified. These tumors exhibit biphasic morphology, with a component resembling pilocytic astrocytoma admixed with variable numbers of small cells forming compact rosettes and perivascular pseudorosettes. Targeted sequencing revealed a 100% co-occurrence of novel and previously described genetic alterations in the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling pathways, suggesting a synergistic role in tumor formation. The most common recurrent mutation, PIK3CA H1047R, was identified in tumor cells forming rosettes and perivascular pseudorosettes. A review of the literature revealed 16 additional cases of rosette-forming glioneuronal tumors in the pineal region. Although rare, this distinctive low-grade tumor warrants consideration in the differential diagnosis of pineal region lesions.

Pineal Cyst Apoplexy in an 8-Year-Old Girl: Case Report and Literature Review

BACKGROUND

Pineal cysts are common, typically asymptomatic, and are usually found incidentally in adults. In rare cases, pineal cyst apoplexy occurs as a result of an acute cystic hemorrhage. This situation can result in acute onset of severe headaches, acute obstructive hydrocephalus, mass effect on the midbrain, and even death. Pineal apoplexy is most common in women of reproductive age, whereas pediatric cases continue to be less prevalent. Pineal cyst apoplexy remains a rare entity with ≥30 cases presented in the literature to date.

CASE DESCRIPTION

We present the youngest case in the literature (an 8-year-old girl with a pineal cyst that resulted in apoplexy), her diagnostic workup, management, and follow-up. We supplement our case study with a literature review of pineal cyst apoplexy.

CONCLUSIONS

Pineal cyst apoplexy remains a rare clinical event in the pediatric population. Our case details the diagnosis and management of an 8-year-old girl with pineal cyst apoplexy. We also discuss our findings from our literature search for all reported cases of pineal cyst apoplexy.

Intravascular Papillary Endothelial Hyperplasia of the Pineal Region: A Case Report and Review of the Literature

BACKGROUND

Intravascular papillary endothelial hyperplasia (IPEH) is a benign vascular lesion that is uncommon in the central nervous system. To our knowledge, there has been only one previous report of occurrence in the pineal region. We present a second case and a review of the literature.

CASE DESCRIPTION

A 28-year-old woman presented with 1 month of headaches and visual auras. Brain magnetic resonance imaging scan demonstrated a 2.6- × 1.8- × 1.3-cm nonenhancing T1-hypointense, T2-/fluid-attenuated inversion recovery-hyperintense pineal region mass with cerebral aqueduct obstruction and hydrocephalus. She underwent placement of a right extraventricular drain followed by complete surgical resection. Histologic analysis was consistent with IPEH.

CONCLUSIONS

Although rare, IPEH is an entity that should be considered in the differential diagnosis for intracranial masses with radiographic features characteristic of vascular lesions. Tissue sampling is imperative for distinction from more malignant entities. Complete resection is curative and is the standard of care when feasible. Given the risk of local progression and neurologic compromise with subtotal resection of central nervous system lesions, further study regarding adjuvant treatment options is warranted.

Reprint of: Signaling the Unfolded Protein Response in primary brain cancers

The Unfolded Protein Response (UPR) is an adaptive cellular program used by eukaryotic cells to cope with protein misfolding stress in the Endoplasmic Reticulum (ER). During tumor development, cancer cells are facing intrinsic (oncogene activation) and extrinsic (limiting nutrient or oxygen supply; exposure to chemotherapies) challenges, with which they must cope to survive. Primary brain tumors are relatively rare but deadly and present a significant challenge in the determination of risk factors in the population. These tumors are inherently difficult to cure because of their protected location in the brain. As such surgery, radiation and chemotherapy options carry potentially lasting patient morbidity and incomplete tumor cure. Some of these tumors, such as glioblastoma, were reported to present features of ER stress and to depend on UPR activation to sustain growth, but to date there is no clear general representation of the ER stress status in primary brain tumors. In this review, we describe the key molecular mechanisms controlling the UPR and their implication in cancers. Then we extensively review the literature reporting the status of ER stress in various primary brain tumors and discuss the potential impact of such observation on patient stratification and on the possibility of developing appropriate targeted therapies using the UPR as therapeutic target. This article is part of a Special Issue entitled SI:ER stress.

Signaling the Unfolded Protein Response in primary brain cancers

The Unfolded Protein Response (UPR) is an adaptive cellular program used by eukaryotic cells to cope with protein misfolding stress in the Endoplasmic Reticulum (ER). During tumor development, cancer cells are facing intrinsic (oncogene activation) and extrinsic (limiting nutrient or oxygen supply; exposure to chemotherapies) challenges, with which they must cope to survive. Primary brain tumors are relatively rare but deadly and present a significant challenge in the determination of risk factors in the population. These tumors are inherently difficult to cure because of their protected location in the brain. As such surgery, radiation and chemotherapy options carry potentially lasting patient morbidity and incomplete tumor cure. Some of these tumors, such as glioblastoma, were reported to present features of ER stress and to depend on UPR activation to sustain growth, but to date there is no clear general representation of the ER stress status in primary brain tumors. In this review, we describe the key molecular mechanisms controlling the UPR and their implication in cancers. Then we extensively review the literature reporting the status of ER stress in various primary brain tumors and discuss the potential impact of such observation on patient stratification and on the possibility of developing appropriate targeted therapies using the UPR as therapeutic target.

Pediatric papillary tumors of the pineal region: to observe or to treat following gross total resection?

INTRODUCTION

Papillary tumors of the pineal region (PTPR) are rare brain tumors characterized by frequent local recurrences. Standardized treatment strategies are not yet defined.

CASE REPORT

We present the case of a 3-year-old girl diagnosed with PTPR. Due to her young age, adjuvant radiotherapy was omitted after gross total tumor resection. Thirty-six months later, local tumor recurrence occurred. Considering the possible risks of secondary surgery, the recurrent tumor was irradiated with proton radiotherapy. Three months later, the tumor showed near-complete remission.

DISCUSSION

Based on this experience and other pediatric case reports from the literature, local radiotherapy might be suggested also after complete tumor resection.

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.

CRX is a diagnostic marker of retinal and pineal lineage tumors

Background

CRX is a homeobox transcription factor whose expression and function is critical to maintain retinal and pineal lineage cells and their progenitors. To determine the biologic and diagnostic potential of CRX in human tumors of the retina and pineal, we examined its expression in multiple settings.

Methodology/Principal Findings

Using situ hybridization and immunohistochemistry we show that Crx RNA and protein expression are exquisitely lineage restricted to retinal and pineal cells during normal mouse and human development. Gene expression profiling analysis of a wide range of human cancers and cancer cell lines also supports that CRX RNA is highly lineage restricted in cancer. Immunohistochemical analysis of 22 retinoblastomas and 13 pineal parenchymal tumors demonstrated strong expression of CRX in over 95% of these tumors. Importantly, CRX was not detected in the majority of tumors considered in the differential diagnosis of pineal region tumors (n = 78). The notable exception was medulloblastoma, 40% of which exhibited CRX expression in a heterogeneous pattern readily distinguished from that seen in retino-pineal tumors.

Conclusions/Significance

These findings describe new potential roles for CRX in human cancers and highlight the general utility of lineage restricted transcription factors in cancer biology. They also identify CRX as a sensitive and specific clinical marker and a potential lineage dependent therapeutic target in retinoblastoma and pineoblastoma.