Pineal region glioblastomas display features of diffuse midline and non-midline gliomas.

Abstract

Introduction.

Pineal region glioblastomas (GBM) are very rare, with approximately 46 cases described in the literature. The epidemiology, pathogenesis, and treatment of these lesions are poorly characterized.

Methods.

We identified all cases of pineal region GBM treated surgically at our institution between 1990 and 2017. Demographic and clinical follow-up data were extracted from the medical records for all cases. Pathology was reviewed and classified according to 2016 World Health Organization (WHO) criteria. Specific attention was given to the frequency of histone H3 K27M mutations in these midline gliomas.

Results.

Eight patients (seven men, one woman) with pineal region GBM, WHO grade IV, were identified. The most common presenting symptoms were headache (75%), vision changes (75%), and gait imbalance/ataxia (50%). Median age at diagnosis was 48.5 years (range: 36 – 74 years). Radical subtotal resection, via a supracerebellar infratentorial approach, was achieved in 75% of patients. Review of the surgical pathology revealed seven primary GBMs (including one giant cell GBM) and one pineal region GBM that developed three years after resection of a pineal parenchymal tumor of intermediate differentiation. No cases demonstrated evidence of IDH-1 R132H mutation (N = 6) or lp/19q co-deletion (N = 3). One case tested positive for the histone H3 K27M-mutation. Targeted exome sequencing of 467 cancer-related genes revealed nonsense mutations in ATRX and NF1. Adjuvant radiation and chemotherapy was employed in 87.5% and 75.0% of patients, respectively. Median overall survival (OS) was 15 months (range: 2 – 24 months) from GBM diagnosis.

Conclusions.

This study expands the clinical and pathologic spectrum of pineal region GBM, and provides the first report of the genetic landscape of these tumors.

INTRODUCTION

The pineal region gives rise to a variety of neoplastic and non-neoplastic lesions of varying malignant potential. Despite this variety however, pineal region tumors in general remain rare and account for less than 1% of all intracranial malignancies [1]. As a result, few published reports focus on specific pineal pathology such as diffusely infiltrating gliomas arising within the pineal region [2–40].

In particular, while glioblastoma (GBM) is the most common primary malignant tumor arising within the brain, clinical and histopathological characterization of pineal region GBM has largely been derived from case reports and small series, as well as extrapolated from individual cases published within larger series. As a result, only 46 cases of pineal region GBM have been described in the literature to date [2–40]. Although consensus suggests neurosurgical intervention remains a fundamental component of multidisciplinary approaches to the diagnosis and management of pineal region lesions, the surgical treatment of pineal region GBM and an evaluation of the importance of newly emphasized molecular features remains to be specifically addressed [41–45].

In 2016, the World Health Organization (WHO) restructured the classification of central nervous system (CNS) diffusely infiltrative glioma utilizing genotype, including IDH-mutation and 1p/19q-codeletion status, and phenotype to diagnose nearly all tumors as either an astrocytoma or an oligodendroglioma [46]. Included in the restructuring of diffuse gliomas is a new entity known as the diffuse midline glioma, H3 K27M-mutant characterized by K27M mutations in the histone H3 gene H3F3A, or less commonly in the related HIST1H3B gene, a diffuse growth pattern, and a midline location such as within the brainstem (especially the pons), spinal cord, or thalamus [46]. This newly defined entity includes tumors previously referred to as diffuse intrinsic pontine gliomas (DIPG), and primarily occurs in children [47–48]. Adults harboring histone H3 K27M mutations have been identified, and at least two cases of a pineal region glioma with H3 K27M mutation have been identified [39,49]. However, the clinical implications of the H3 K27M mutation remain to be determined.

We retrospectively identified eight histopathologically confirmed cases of GBM arising within the pineal region treated at a single institution between 1990 and 2017. Clinical and pathologic features are presented, along with a review of the literature of these very rare lesions.

METHODS

Clinical data and outcome assessments

Demographic and clinical follow-up data were extracted from the medical records for all cases. Extent of resection (EOR) was determined from review of postoperative magnetic resonance imaging (MRI) and radiology reports. Radical subtotal resection (r-STR) refers to the gross total resection of contrast-enhancing tumor as determined on postoperative MRI performed within 48 horns of surgery given the understanding that residual infiltrative and unresectable tumor cells invariably persist following removal of diffusely infiltrating gliomas. Subtotal resection (STR) refers to any incompletely resected lesion as determined by the presence of residual contrast-enhancing tumor on post-operative MRI performed within 48 hours of surgery. Biopsy refers to cases in which only small amounts of tissue were obtained for the purpose of diagnosis with no attempt at resection. Overall survival (OS) was defined as the duration of time from each patient’s most definitive surgery to the date of death, or to the most recent clinical or radiographic evaluation for one patient lost to follow up shortly after discharge. OS of one patient who initially presented with PPTID and progressed to GBM was evaluated from initial GBM diagnosis.

Histopathological review

All aspects of this study were approved by the Columbia University Medical Center (CUMC) Institutional Review Board (IRB). All pineal region tumors treated surgically by a single surgeon (JNB) at CUMC between 1990 and 2017 were retrospectively reviewed for diagnoses consistent with diffusely infiltrative glioma, WHO II-IV. All cases underwent histopathological re-evaluation by a neuropathologist (GZ) based on 2016 WHO grading criteria [46]. Eight cases of histopathologically confirmed WHO grade IV GBM were subsequently identified and included in this analysis.

Immunohistochemical staining

Immunohistochemistry was performed on formalin-fixed, paraffin-embedded tissue sections at the CUMC Department of Pathology and Cell Biology Laboratory. Histological analysis of tumor specimens was done with Hematoxylin & Eosin (H&E) staining. Immunoperoxidase staining was done on paraffin-embedded sections using antibodies to Ki67, IDH1-R132H, ATRX, p53 (all from Ventana, Tucson, AZ), and histone H3 K27M (Millipore Sigma, Billerica, MA). A neuropathologist (GZ) evaluated the histology. Pathology reports were reviewed for additional histological analyses performed during routine clinical pathological evaluation at the time of initial diagnosis.

Targeted next-generation sequencing

Tissue for sequencing was obtained from formalin-fixed, paraffin-embedded sections. DNA was purified, and exons from 467 cancer-related genes were captured using Agilent SureSelect reagents (Santa Clara, CA). Sequencing was performed on the Illumina HiSeq2500 platform (San Diego, CA). Variants were filtered after referencing OMIM, 1000 Genomes Project, dbSNP, Exome Variant Server, and a CUMC database of common variants.

Additional molecular tests

For determination of EGFRvIII (EGFR r.89_889del) expression, RNA was extracted from formalin-fixed, paraffin-embedded tissue. Complementary DNA (cDNA) was synthesized by reverse-transcriptase and amplified with primers designed specifically to amplify either EGFRvIII or GAPDH. The MGMT promoter methylation assay is also PCR-based, with tumor DNA extracted from formalin-fixed, paraffin-embedded tissue and tested for the presence of hypermethylation of the MGMT promoter in region +28 to +47 from the translation start site in exon 1. Examination of chromosome 1p19q was performed with two independent DNA probes- LSI 1p36 (TP73)/LSI 1q25 (ANGPTL1) and LSI 19q13 (GLTSCR1)/LSI 19p13 (ZNF443). Fluorescent in situ hybridization with these two probes, and probes directed against the centromeres of each chromosome, was performed on thick sections cut from formalin-fixed, paraffin-embedded tissue. A cut-off of 7–9% was defined as deletion for each individual probe.

RESULTS

Patient, tumor, and treatment characteristics

Eight cases (3.7%) of pineal region GBM were identified out of 215 pineal region tumors treated by a single surgeon (JNB) between 1990 and 2017. Patient, tumor, and treatment characteristics are presented in Table 1. The median age at diagnosis for all patients was 48.5 years (range: 36 – 74 years) and 87.5% of patients were male. The most common presenting symptoms were headache (75%), vision changes (75%), and gait imbalance/ataxia (50%). Tumor origin was believed to be within the pineal gland (37.5%) or the thalamus (37.5%), as determined by comparison of preoperative imaging and operative reports documenting regions of tumor attachment and infiltration (Figure 1). Notably, tumor origin was felt to be indeterminate in two (25%) cases given the extent of invasion and involvement of adjacent structures.

Table 1.

Patient and Operative Characteristics

Characteristics	No. (%)
No. Cases	8
Age (yr)
Median	48.5
Range	(36-74)
Sex (%)
Male	7 (87.5)
Female	1 (12.5)
Tumor Size (cm)
Mean	2.7
Range	(2.0-3.6)
No. Patients with Hydrocephalus	7 (87.5)
No. VPS	2 (28.6)
No. Shunt Malfunction	1 (50.0)
No. ETV	5 (71.4)
No. ETV Malfunction	2 (40.0)
Initial Surgical Approach
SCIT	8 (100.0)
Site of tumor origin
Midbrain tectum	0 (0.0)
Pineal gland	2 (25.0)
Thalamus	3 (37.5)
Indeterminate	3 (37.5)
Length of Stay (days)
Median	7.5
Range	(3 - 34)
Initial Surgical Approach
SCIT	8 (100)
Extent of Resection
r-STR	6 (75.0)
STR	2 (25.0)
Bx	0 (0.0)
Radiation	7 (87.5)
Chemotherapy	6 (75.0)
Progression/Recurrence	6 (75.0)
Distal Recurrence	1 (16.7)
Reoperations*	2 (25.0)
Death at last follow-up**	7 (87.5)

SCIT = supracerebellar infratentorial; r-STR = gross total resection; STR = subtotal resection; Bx = biopsy; VPS = ventriculoperitoneal shunt; ETV = endoscopic third ventriculostomy; SCIT = supracerebellar infratentorial.

^*Reoperation was for local recurrence in one patient and distal recurrence in one patient.

^**One patient was lost to follow up immediately following initial discharge.

Figure 1.

Radiographic and histologic features of pineal region GBM. Representative sagittal (A) and axial (B) contrast-enhanced T1-weighted MRI of pineal region GBM (Case ID: P-148) demonstrates a heterogeneously enhancing mass originating within the pineal gland and extending into the posterior third ventricle, causing local mass effect on the posterior thalamus bilaterally and obstruction of the aqueduct of Sylvius with associated hydrocephalus. The mass demonstrates T2/FLAIR hyperintensity on FLAIR MRI (C), and mild restricted diffusion (D). GTR was considered the complete removal of all contrast-enhancing tumor as depicted on post-operative contrast-enhanced MRI (E). Representative H&E-stained sections of a pineal GBM (Case ID: P-216) show a diffusely infiltrating neoplasm with areas of high cellularity, pseudopalisading necrosis (F, star), and glomeruloid vascular proliferation (G, arrows highlight a portion of one such blood vessel). A GFAP immunostain is strongly positive in the tumor and negative in the blood vessels (H). A Ki67 stain demonstrating elevated proliferation, with up to 40.5% of cells staining positive (I). In one pineal tumor (Case ID: P-218), strong nuclear staining is seen in many cells with an anti-H3K27M antibody that recognizes this mutation in histone H3.1 and H3.3 (J).

Hydrocephalus was the cause of the presenting symptoms in 7 (87.5%) patients and was managed by preoperative endoscopic third ventriculostomy (ETV) in 5 (71.4%) patients and by ventriculoperitoneal shunt (VPS) insertion in 2 (28.6%) patients (Table 1). No patient demonstrated evidence of spinal metastases, while one patient (Patient ID: P-218) did show evidence of diffuse seeding of the ventricular system with tumor at the time of surgery.

Median and mean OS was calculated from 7 of 8 patients following GBM diagnosis and was 15 months, respectively (range: 2 – 24 months), during which time all tumors recurred and/or progressed despite EOR or adjuvant therapy except in one patient who died from perioperative complications prior to documented radiographic recurrence (Patient ID: P-128).

Tumors recurred locally in all cases except in one (12.5%) patient who underwent resection of a pineal region GBM of thalamic origin and ultimately developed distal recurrence within the right frontal lobe requiring multiple operative interventions prior to dying from disease progression 24 months after diagnosis.

Table 2 demonstrates the relevant clinical features of all eight identified cases of pineal region GBM. With respect to treatment, r-STR was achieved in 75% of patients. STR was achieved in 25% and no patient underwent biopsy alone. Although the number of cases failed to meet the threshold for robust outcomes analysis, median OS for patients undergoing r-STR was 15 months (range: 2 - 24 months) as compared with an OS of 10 and 23 months in the two patients undergoing STR. Perceived tumor origin within the thalamus or pineal gland did not appear to influence the ability to achieve r-STR (Table 2).

Table 2.

Clinical features of 8 pineal region GBMs.

Pineal ID	Age (yrs)	Gender (m, f)	Tumor size (cm)	Tumor Origin	Hydroce phalus (Y, N)	ETV, VPS, EVD, None	No. Surgeries	Initial surgical approach	EOR (r-STR vs. STR)	XRT	Temodar	Adjuvantchemo	OS (months)
P-023	51	m	3.50	Indeterminate	Y	VPS	1	SCIT	r-STR	Y	Y	Cisplatin	LTFU
P-128	52	m	2.30	Thalamus	Y	ETV	1	SCIT	r-STR	N	N		2
P-148	38	m	2.00	Pineal	Y	ETV	1	SCIT	r-STR	Y	Y		20
P-196*	51	m	2.00	Thalamus	Y	ETV	3	SCIT	r-STR	Y	Y	DCA, KPT-330, avastin	24
P-198**	46	f	3.60	Indeterminate	N	None	2	SCIT	r-STR	Y	Y		54 (15)
P-210	74	m	2.30	Pineal	Y	VPS	1	SCIT	r-STR	Y (40Gy)	Y	Optune, nivolumab	8
P-216	36	m	2.60	Thalamus	Y	ETV	1	SCIT	STR	Y	N		10
P-218	38	m	3.00	Indeterminate	Y	ETV	1	SCIT	STR	Y	Y		23

ETV = endoscopic third ventriculos tomy; VPS= ventriculop eritoneal shunt; EVD = external ventricular drain; SCIT = supracereb ellar infratentorial; r-STR = radical subtotal resection; STR = Subtotal resection; LTFU = lost to follow up; DCA = dichloroacetate; OS = overall survival; EOR = extent of resection.

^*The patient Underwent two additional right frontal craniotomies for distal recurrence.

^**This patient initially presented with a PPTID (III) which was treated with resection via SCIT approach. Subsequent recurrence was consistent with GBM for which the patient underwent an interhemispheric transcallosal approach with subsequent GTR. Survival following GBM diagnosis was 15 months.

All GBM patients received adjuvant radiation and chemotherapy except one patient (Patient ID: P-128) who died from perioperative complications prior to initiating any adjuvant treatment, and another patient (Patient ID: P-216) who received radiation, but did not qualify for chemotherapy given significant medical contraindications (Table 2). All GBM patients who received adjuvant radiation were treated with the standard hypofractionated external beam radiotherapy (EBRT) to a median dose of 60 Gy, except one elderly patient (Patient ID: P-210) who received 40 Gy. All patients who ultimately received chemotherapy were initially treated with temozolomide. Additional chemotherapies were attempted in three (37.5%) patients. Patients who received additional chemotherapy were treated with Avastin (12.5%), Cisplatin (12.5%), Nivolumab (12.5%), KPT-330 (12.5%), and dichloroacetate (12.5%). One (12.5%) patient underwent treatment with Optune in addition to standard treatment (Table 2).

Histopathological review

Seven of the eight resection specimens were re-reviewed (slides from case P-023 were not available, and diagnosis was based on initial pathological review). All reviewed cases fit morphologic criteria for GBM—namely, hypercellularity, nuclear atypia, increased mitotic activity, necrosis (Figure 1 F) without or with glomeruloid vascular proliferation (Figure 1G). Abundant GFAP expression was noted in the neoplastic cells (Figure 1H). One case, P-148, showed features of a giant cell GBM. No gliosarcomas or epithelioid GBM were noted.

In addition to histopathologic characteristics, the 2016 WHO criteria for GBM include IDH mutation status. A histopathological review of molecular markers is presented in Table 3. IDH-1 mutations were not identified in six patients with available IDH-1 R132H mutation status. The mean Ki67 index was 24.3% (range: 5.2% - 50%) in seven patients. Maintenance of ATRX was identified in one (20%) patient (Patient ID: P-198), while expression was lost in the remaining available cases reviewed (N = 5). No examined cases demonstrated evidence of lp/19 co-deletion (N = 3), MGMT promoter methylation (N = 4), or expression of EGFRviii (N = 4). One case (described below) tested positive for the H3 K27M-mutation.

Table 3.

Histopathological profile of pineal region GBMs.

Pineal ID	Ki67	IDH-1 status (wt, m)	Loss of ATRX	1p/19q co-deletion	MGMT methylation	EGFRviii	H3 K27M
P-023	-	-	-	-	-	-	-
P-128	5.2%	wt	lost in most cells	-	-	negative	negative
P-148	50.0%	-	-	-	-	-	-
P-196	40.0%	wt	maintained	negative	unmethylated	negative	negative
P-198	12.0%	wt	lost	-	unmethylated	negative	negative
P-210	13.2%	wt	lost	negative	unmethylated	negative	negative
P-216	40.5%	wt	lost	negative	unmethylated	test failed	negative
P-218	9.3%	wt	lost	-	-	-	positive

wt = wildtype; m = mutant; - = not performed.

Targeted next-generation sequencing

Two cases (Patient IDs: P-210 and P-216) had sequencing data available. Targeted sequencing of P-216 revealed a nonsense mutation (c. 1252C >T, p.R418*) in ATRX that truncates the last 2075 amino acids of the protein. This mutation has been previously reported in one case of glioma in the catalogue of somatic mutations in cancer (COSMIC) database [50,51], and is consistent with the loss of wildtype ATRX by immunocytochemistry in this patient. In addition, a nonsense mutation (c.6855C >A, p.Y2285*) in NF1 that truncates the last 555 amino acids of the protein was identified. This mutation has similarly been reported in COSMIC in a lung neoplasm and a malignant peripheral nerve sheath tumor. Additional variants of uncertain significance included variants in TP53, PTEN, ERCC2, CLTCL1, FGFR3, SPEN and RPS6KB2.

In the second case (P-210), novel frameshift mutations in ATRX (c.3855delC, p.S1286Lfs) and NF1 (c.6493_6520del28, p.F2165Lfs) were identified, as well as an activating mutation of FGFR1 (c.1731C>A; p.N577K) that is common in gliomas according to the COSMIC database. Additional variants of uncertain significance were seen in CHEK2, ARID1B, MLL3, NCOR1, and LAMB4.

Selected case reports

H3 K27M-mutation

One case (Patient ID: P-218) tested positive for the H3 K27M-mutation. Briefly, a 38-year-old male presented initially with headache, ataxia, and vision changes, and was discovered to have a contrast-enhancing pineal lesion predominantly within the pineal gland, but with extensive thalamic invasion, as well as diffuse seeding of the ventricular system with enhancing tumor. The patient underwent STR with estimated removal of 65-75% of the tumor given the extensive invasion of the adjacent thalamus and ventricular tumor burden at the time of surgery.

Histopathological review of the tissue confirmed a highly cellular astrocytic tumor with marked nuclear atypia, occasional mitoses, vascular proliferation, and a small focus of necrosis. Immunohistochemical analysis was notable for an IDH-1 R132H wildtype tumor, with associated loss of ATRX. The tumor did test positive for H3 K27M mutation by immunocytochemistry (Table 3; Figure 1J). The Ki67 proliferation index was noted to be 9.3%.

The patient subsequently underwent standard adjuvant therapy consisting of hypofractionated radiation (60 Gy) and temozolomide, as well as additional cycles of adjuvant temozolomide. Ultimately, while the patient demonstrated evidence of progression at one month, he survived a total of 23 months before dying from disease progression.

Recurrence of PPTID as GBM

A second case (Patient ID: P-198) deserves specific mention as it represents the progression of a previously resected PPTID, WHO grade III—originally treated 3-years prior with r-STR and adjuvant radiation—to GBM (Figure 2). Briefly, a 43-year-old woman presented initially with a hemorrhagic pineal region mass without associated hydrocephalus. The 2.2 cm lesion was heterogeneously contrast-enhancing on MR imaging, and demonstrated heterogeneous hyperintensity on FLAIR/T2-weighted MRI sequences. The lesion notably arose from the pineal gland and extended into the splenium of the corpus callosum causing local mass effect on the third ventricle and left lateral ventricle and lateral displacement of the internal cerebral veins to the right. The patient underwent r-STR via a supracerebellar infratentorial (SCIT) approach (Figure 2A–E).

Figure 2.

Case P-198 of a PPTID, WHO grade III recurring as GBM. Representative sagittal (A) and axial (B) contrast-enhanced, T1-weighted MRI demonstrating a heterogeneously enhancing mass originating within the pineal gland and extending into the splenium of the corpus callosum causing local mass effect on the third ventricle and left lateral ventricle and displacing the internal cerebral veins to the right. The mass demonstrates T2/FLAIR hyperintensity on FLAIR MRI (C), and mild restricted diffusion (D). GTR was achieved via a supracerebellar, infratentorial approach as depicted on post-operative MRI (E). Representative sagittal (F) and axial (G) contrast-enhanced, T1-weighted MRI demonstrates a recurrent, rim-enhancing mass at the level of the pineal gland extending superiorly and displacing the splenium of the corpus callosum. The recurrent lesion again demonstrated T2/FLAIR hyperintensity on FLAIR MRI (H) and mild restricted diffusion (I). GTR was achieved via an interhemispheric, transcallosal surgical approach with removal of all contrast-enhancing residual tumor as determined on postoperative MRI (J). (K) H&E demonstrates neoplastic cells with round nuclei, speckled chromatin and variable amounts of eosinophilic cytoplasm. The neoplastic cells are strongly positive for synaptophysin (L). A GFAP immunostain predominantly highlights reactive, interstitial astrocytes (M). (N) H&E demonstrating atypical, highly pleomorphic cells with irregular, hyperchromatic nuclei. Synaptophysin is weakly positive in tumor cells, but not in glomeruloid vasculature (arrows; O). GFAP stain demonstrating diffuse strong positive staining in most areas (P).

Pathology from 2013 was reviewed and clearly demonstrates phenotypical and immunohistochemical features consistent with a diagnosis of PPTID (Figure 2K–M). Neoplastic tissue was moderately cellular and composed of relatively uniform cells with a round nuclear shape, speckled chromatin, and variable amounts of eosinophilic cytoplasm, with up to 10 mitotic figures identifiable in 10 high-power fields. Immunohistochemical analyses demonstrated strong staining of neoplastic cells with synaptophysin, absence of neurofilament (data not shown) and an elevated Ki67 proliferation index, with up to 12% of cells staining positive. Based on currently available data, the tumor was put into the classification of higher grade PPTID (WHO grade III) given the high mitotic rate [52]. A majority of the neoplastic cells expressed a glial marker, olig2 (data not shown), which is typically expressed at very low levels in the normal human pineal [53].

Approximately 3 years later, the patient presented with acute onset altered mental status and was discovered again to have a hemorrhagic pineal region mass presumed to represent recurrence of her previously resected tumor. MRI at the time demonstrated a 2.6 cm heterogeneously contrast-enhancing mass lesion at the level of the pineal gland extending upward and displacing the splenium of the corpus callosum. The mass lesion was slightly asymmetric to the right side and in close association with the septum pellucidum. The patient underwent reoperation via an interhemispheric, transcallosal (IHTC) approach given the superior and lateral extent of the recurrence (Figure 2F–J). Pathologic analysis of the recurrence demonstrated a diffusely infiltrating glial neoplasm with areas of pseudopalisading necrosis and clear glomeruloid vascular proliferation consistent with a diagnosis of GBM. While synaptophysin was weakly positive in the tumor, GFAP was strongly positive in the majority of the neoplasm (Figure 2N–P). Olig2 staining was seen in approximately 90% of cells in some areas of the tumor (data not shown). The tumor demonstrated a wildtype IDH-1 R132H status, a loss of ATRX, unmethylated MGMT promoter, no EGFRviii amplification, and no H3 K27M mutation (Table 3).

The patient subsequently underwent standard adjuvant therapy consisting of hypofractionated radiation (60 Gy) and temozolomide. While OS was 54 months following her first surgery, OS was 15 months following resection of the GBM.

DISCUSSION

Glioblastoma (GBM) is the most common primary malignant tumor arising within the brain. However, GBMs arising within the pineal region are rare, with only 46 reported cases in the literature [2–40]. As a result, little is known about the clinical or biological behavior of these tumors other than what can be extrapolated from the data on GBM as a whole. Specific characterization of these rare lesions has thus been largely derived from case reports and small series from single institutions with short follow-up, as well as extrapolated from individual cases published within larger series. Data on pathological or molecular differences between pineal GBMs and those encountered at other locations are limited, and current therapeutic strategies for pineal region GBMs mimic the accepted standard of care [54]. Here we present demographic, clinical, treatment, and histopathologic data from eight patients with pineal region GBMs treated at single institution with one of the largest pineal surgical series by a single surgeon (JNB) over the span of 27 years. Our objective is to provide a more extensive clinical and histopathologic characterization of pineal region GBMs. Particular attention was given to the frequency of histone H3 K27M mutations in these midline gliomas, and we report the occurrence of this mutation in a pineal GBM. In addition, we detail a case of a pineal GBM that occurred in a patient three years after resection of a PPTID. Shared molecular characteristics of the two tumors, including olig2, in this patient raises the possibility of a previously undescribed plasticity of pineal parenchymal tumors.

Pineal region GBMs—and most pineal region lesions—typically present with symptoms related to local mass effect causing obstructive hydrocephalus and related symptoms of headache, nausea/vomiting, gait abnormalities, and vision changes as in this series [3]. In this series, only one patient (Patient ID: P-198) did not receive preoperative CSF diversion. This was likely due to the fact that her tumor projected superiorly exerting mass effect primarily on the splenium as opposed to the quadrigeminal plate and aqueduct of Sylvius. In general, we prefer preoperative ETV to VPS as it avoids complications inherent to permanent shunt insertion.

While we saw a predominance in middle-aged males in this series, previous studies have reported a slightly higher frequency of pineal GBM in middle-aged adult females [3]. Interestingly, while thirteen previously reported cases had evidence of leptomeningeal dissemination, and five had evidence of spinal metastases, only one case (12.5%) in our series had evidence of diffuse seeding of the ventricular system at the time of the initial surgery and no cases demonstrated spinal metastases. Previously published reports have considered an increased risk of leptomeningeal and ventricular dissemination to be an additional risk related specifically to pineal region GBMs given their location [3,5]. Wide dissemination of tumor cells is a poor prognostic indicator and may contribute significantly to the poor prognosis historically associated with pineal region GBM [3].

Notably, median OS in our series was 15 months (range: 2 – 24 months). This varies greatly from the median survival available in published cases of only 6.5 months (range: 0 – 40 months) [2–40]. Unfortunately, published data regarding EOR and therapeutic algorithms utilized in these studies are heterogeneous and difficult to use for clear comparison. Furthermore, 17 previously published cases were identified prior to the landmark paper supporting the use of temozolomide in GBM [4,7–12,14,16–18,20,29,33,34]. It is possible that the widespread use of modem imaging modalities, as well as a modem algorithm for treating pineal disease has improved early identification and treatment of these lesions and thus limited widespread CNS dispersal. Additionally, improved operative techniques and adjuvant therapies may have contributed to prolonged survival for patients harboring GBM. In fact, a recent report of 4 pineal GBMs demonstrated a median OS of 20.5 months (range: 6 – 32 months) supporting that modem treatment algorithms may be improving outcomes [38].

Our study is not powered to provide evidence in support of maximizing EOR for pineal region GBM. While an abundance of data supports safe maximal resection for supratentorial GBM [56]. EOR did not seem to influence survival in our small cohort. Safe, maximal resection with the goal of securing a tissue diagnosis and relieving symptomatic mass effect and associated hydrocephalus—while avoiding permanent damage to critical neurovascular structures—followed by adjuvant chemotherapy and radiation, appears to be effective for the treatment of pineal region GBM regardless of residual tumor burden. However, further studies are necessary to define the influence of these interventions.

Although the number of cases thus failed to meet the threshold for robust outcomes analysis, the data from this cohort, which is the largest group of patients with pineal GBMs, provide evidence that while GBMs arising within the pineal gland or the thalamus appear to display the same molecular phenotypes as other supratentorial GBMs, these midline lesions can also contain H3 K27M mutations otherwise present in diffuse midline gliomas arising within midline structures in both pediatric and young adult patients. While studies have suggested that these H3 K27M mutations are associated with aggressive clinical behavior and poor prognosis [47,57,58], more recent evidence suggests that thalamic gliomas in adult patients with H3 K27M mutations might not be associated with worse prognoses than corresponding H3 wild-type thalamic gliomas, suggesting heterogeneity among this molecular subgroup of diffuse midline gliomas [59–61]. Recognition of this mutation and better characterization of the natural history of tumors harboring these mutations may permit more accurate determinations of prognosis and treatment response in these patients, especially as targeted therapies will soon be in clinical trial for these patients [49,62,63]. Interestingly, while the patient who was found to harbor the H3 K27 mutation was the only patient in this series with diffuse seeding of the ventricles, overall survival reached 23 months after receiving standard of care, supporting evidence that these mutations may not be associated with worse prognosis in adult patients [60].

We also describe the first case of a pineal GBM following r-STR of a PPTID. PPTIDs are rare tumors arising from pineal parenchyma that are considered an intermediate along the spectrum of well-differentiated pineocytoma to undifferentiated pineoblastoma [52]. Histologically, PPTIDs typically demonstrate a lobular or diffuse arrangement of moderately or highly cellular tissue, with mild or moderate nuclear atypia and moderate mitotic activity, as well as nuclear stippling. Necrosis and vascularity are rare, but possible features [64]. Tumor grade is currently decided based on the application of a proposed classification of PPTID according to number of mitoses, presence of necrosis, and the immunolabelling of neurofilament [65]. While PPTID recurrence is not uncommon [66], little is known about the histologic progression of recurrent PPTID although a report of anaplastic transformation into pineoblastomas has been reported [67]. To date, no reports exist documenting transformation of a PPTID into GBM.

At original diagnosis, the described tumor demonstrated clear features of PPTID, including uniform cells with a round nuclear shape, speckled chromatin, and variable amounts of eosinophilic cytoplasm. Immunohistochemical analysis further supported a diagnosis of PPTID with strong staining of neoplastic cells with synaptophysin. Notably, the elevated mitotic rate and Ki67 proliferation index both supported the diagnosis of a WHO Grade III lesion. Interestingly, most of the neoplastic cells expressed olig2 and, to a lesser extent, GFAP. Three years later, the tumor exhibited clear features of GBM including pseudopalisading necrosis and glomeruloid vascular proliferation. Furthermore, the tumor was more uniformly positive for GFAP and olig2, strongly supporting a diagnosis of GBM. This suggests that cellular components of PPTIDs may retain the ability to differentiate along a glial lineage.

Ultimately high-resolution genomic analyses will shed light on these ambiguities and also identify molecular markers that may guide chemotherapeutic decisions for future patients. We present the results of targeted next-generation sequencing for two patients in our series. Notably, mutations in ATRX and NF1 were identified in both cases. ATRX is a DNA helicase that is important in chromatin remodeling and associated with maintenance of telomere length—considered a factor of cell survival and proliferation—in glioma [68]. Preclinical data suggests that ATRX-deficient gliomas grow more aggressively than wild-type ATRX tumors due to more rapid accumulation of oncogenic mutations, and that they may also be more sensitive to adjuvant therapies that induce double strand DNA breaks such as radiation therapy and doxorubicin, irinotecan and topotecan compared to agents that induce single strand DNA breaks such as CCNU and temozolomide [69]. The NF1 gene has emerged in recent years as an important tumor suppressor gene in gliomas, not only in those with a diagnosis of neurofibromatosis, but also in those that develop sporadically. Evidence suggests that alterations in the gene encoding NF1 occur in a subset of diffusely infiltrative gliomas, and that loss of NFt may be associated with worse overall- and disease specific survival in lower-grade gliomas, but not necessarily in GBM [70–72]. Of note, in this series, both cases which harbored alterations in NF1 were examples of aggressive tumors with OS of only 8 and 10 months, despite standard of care treatment. Characterization of the full clinical and biologic significance of ATRX and NF1 genetic loss in diffuse gliomas and its cooperation with other genetic alterations requires further study.

CONCLUSION

Pineal region GBM does not differ significantly from GBM arising elsewhere within the CNS based on morphologic and genetic analysis. While histone H3 K27M mutations are possible in pineal region GBMs, the prognostic significance remains undefined. Our data support the role of safe, surgical intervention with the goals of securing accurate tissue diagnosis and decompressing symptomatic mass effect in pineal region GBM. Similarly, our data support the use of adjuvant radiation and chemotherapy for these lesions. High-grade PPTIDs may retain the ability to transform into malignant gliomas.

Abbreviations

GBM

glioblastoma

WHO

World Health Organization

CNS

central nervous system

PPTID

pineal parenchymal tumor of intermediate differentiation

CUMC

Columbia University Medical Center

IRB

Institutional Review Board

MRI

magnetic resonance imaging

r-STR

radical subtotal resection

STR

subtotal resection

OS

overall survival

EBRT

external beam radiotherapy

SCIT

supracerebellar infratentorial

IHTC

interhemispheric transcallosal

COSMIC

catalogue of somatic mutations in cancer

OMIM

Online Mendelian Inheritance in Man

dbSNP

single nucleotide polymorphism database