Synchronous pineal and suprasellar pineoblastoma in a child mimicking bifocal germinoma

Abstract

Bifocal pineal and suprasellar lesions in children are classically associated with intracranial germinoma, and empirical treatment without histological confirmation has been advocated in selected protocols. Pineoblastoma, however, is a rare and highly aggressive embryonal tumor requiring fundamentally different management. We report the case of a 10-year-old girl who presented with signs of subacute intracranial hypertension. Brain magnetic resonance imaging (MRI) demonstrated synchronous pineal and suprasellar masses associated with obstructive hydrocephalus. Both lesions were isointense on T1- and T2-weighted sequences and exhibited homogeneous contrast enhancement. Serum and cerebrospinal fluid levels of alpha-fetoprotein and β-human chorionic gonadotropin were within normal limits. Given the characteristic bifocal distribution and negative tumor markers, a presumptive diagnosis of bifocal germinoma was initially considered. The patient underwent endoscopic third ventriculostomy with tumor biopsy, which unexpectedly revealed a pineoblastoma (WHO grade 4). Although her clinical condition initially improved and craniospinal irradiation was planned, she developed recurrent acute hydrocephalus and died 6 weeks later. This case highlights the limitations of relying solely on imaging features and tumor markers when evaluating bifocal pineal and suprasellar lesion. Histopathological confirmation remains essential to avoid misdiagnosis and inappropriate treatment of aggressive tumors such as pineoblastoma.

Introduction

Pineoblastoma is a rare, highly malignant embryonal tumor originating from pineal parenchymal cells and classified as a World Health Organization (WHO) grade IV neoplasm [1,2]. It accounts for less than 1% of pediatric intracranial tumors and predominantly affects children [3]. The disease is characterized by rapid growth, early cerebrospinal fluid dissemination, and an overall poor prognosis despite aggressive multimodal therapy [4,5].

In contrast, synchronous pineal and suprasellar lesions are most commonly associated with intracranial germinomas [6]. In the presence of normal serum and cerebrospinal fluid tumor markers, this bifocal pattern has often been considered sufficient to support treatment initiation without histological confirmation [7,8]. However, this empirical approach carries risks, as the therapeutic strategies and outcomes differ dramatically between germinomas and other malignant pineal region tumors [9].

Radiological differentiation between germinoma and pineoblastoma remains difficult, as both tumors may exhibit overlapping MRI features, including similar signal characteristics and contrast enhancement patterns [10]. Although lesion morphology and diffusion-weighted imaging parameters may provide diagnostic clues, substantial overlap limits their reliability, making imaging alone insufficient for definitive diagnosis [11,12].

To date, there is only 1 report of 2 pediatric cases of non–germ cell tumors presenting with bifocal involvement of the pineal and suprasellar regions [13]. We describe a rare case of synchronous pineal and suprasellar pineoblastoma in a 10-year-old girl, highlighting the critical importance of histological confirmation to prevent misdiagnosis and inadequate treatment.

Case description

A previously healthy 10-year-old girl presented with a 2-month history of progressively worsening headache, recurrent vomiting, gait instability, visual impairment, and lethargy. There was no history of diabetes insipidus or other endocrine disturbances. Neurological examination revealed bilateral abducens nerve palsy, Parinaud’s syndrome, and a positive Romberg sign. Ophthalmological assessment demonstrated markedly reduced visual acuity, limited to light perception in the left eye, bilateral papilledema, and optic disc pallor on the left side.

Brain MRI demonstrated a well-circumscribed pineal region mass measuring 27 × 21 × 17 mm causing aqueductal obstruction and hydrocephalus, along with a smaller suprasellar lesion measuring 5 × 8 × 10 mm (Fig. 1). Both lesions were isointense to gray matter on T1-, T2-, and FLAIR-weighted images and exhibited avid homogeneous contrast enhancement. The pineal mass showed marked diffusion restriction with corresponding low apparent diffusion coefficient values. No evidence of intratumoral hemorrhage, cystic change, calcification, or perilesional edema was observed. No additional intracranial lesions were identified, and contrast-enhanced spinal MRI revealed no evidence of leptomeningeal dissemination or drop metastases. Serum and cerebrospinal fluid (CSF) alpha-fetoprotein and β-human chorionic gonadotropin levels were within normal limits. Endocrine investigations and electrolyte analyses were unremarkable.

Fig. 1.

Brain MRI. sagittal (A) and axial (B, C) postcontrast T1-weighted images demonstrate enhancing lesions in the pineal region (yellow arrow) and the suprasellar region (white arrow). Both lesions appear isointense on T2-weighted imaging (D) and Diffusion-weighted imaging (E) showed diffusion restriction of the pineal lesion.

The bifocal pineal-suprasellar pattern, homogenous characteristics on conventional MRI sequences and normal tumor markers initially favored a diagnosis of bifocal germinoma.

The patient underwent emergency endoscopic third ventriculostomy. The suprasellar lesion was selected for biopsy because it protruded into the anterior recess of the third ventricle and was readily accessible through the endoscopic trajectory used for third ventriculostomy (Fig. 2), whereas the pineal lesion could not be safely reached through the same approach. CSF obtained during the endoscopic procedure was submitted for cytological examination and tumor marker analysis. Cytology assessment revealed no malignant cells. The postoperative course was initially favorable, with significant neurological improvement. Histopathological examination of the suprasellar lesion revealed a dense proliferation of small round blue cells with hyperchromatic nuclei and scant cytoplasm. Immunohistochemical analysis showed strong synaptophysin expression, a high Ki-67 proliferation index, and negativity for GFAP and OCT4, consistent with pineoblastoma (Fig. 3). The diagnosis was confirmed by an independent pathological review. Molecular analysis was not available.

Fig. 2.

Endoscopic view of the anterior recess of the third ventricle showing a lesion (yellow star) protruding into the ventricular cavity.

Fig. 3.

Histopathological findings. Hematoxylin–eosin staining shows a densely cellular tumor composed of small round blue cells (A). Immunohistochemical analysis demonstrates synaptophysin positivity (B) and a high Ki-67 labeling index (C).

Craniospinal irradiation combined with multiagent chemotherapy was subsequently planned. Six weeks later, during the early phase of radiotherapy, the patient acutely deteriorated, presenting with sudden loss of consciousness, a Glasgow Coma Scale score of 3, and bilateral fixed mydriasis. Computed tomography demonstrated recurrent acute hydrocephalus. Despite emergency external ventricular drainage, the patient died. Obstruction of the ventriculostomy stoma due to rapid suprasellar tumor progression was considered the most likely cause.

Discussion

Bifocal involvement of the pineal and suprasellar regions has traditionally been regarded as a hallmark of intracranial germinoma, particularly in the setting of normal serum and CSF tumor markers and diabetes insipidus [6]. This paradigm has led to treatment strategies that occasionally bypass histological confirmation [7,8]. The present case clearly illustrates the limitations of such an approach.

Isolated adult cases of bifocal involvement of the pineal and suprasellar regions have been reported in the context of metastatic disease and papillary tumors of the pineal gland [[14], [15], [16]]. In comparison, pediatric cases of non–germ cell tumors presenting with synchronous pineal and suprasellar lesions remain exceptional. To date, only 2 such pediatric cases have been reported, both classified within the spectrum of primitive neuroectodermal tumors [13]. Our observation further expands this limited experience by documenting a pineoblastoma, highlighting this entity as a potential diagnostic pitfall in bifocal pineal–suprasellar presentations.

Radiological differentiation between germinoma and pineoblastoma is often challenging. Both tumors may demonstrate similar signal characteristics and contrast enhancement patterns on MRI [10].

However, several imaging features have been proposed to aid in differentiation.

Pineoblastomas tend to be more irregularly shaped and invasive, often involving adjacent structures such as the tectum and thalamus [12]. They typically demonstrate more marked diffusion restriction on diffusion-weighted imaging, reflecting their high cellularity, with correspondingly lower apparent diffusion coefficient (ADC) values compared to germinomas. Quantitative ADC analysis has shown promise in distinguishing pineal germ cell tumors from pineoblastomas, with pineoblastomas generally exhibiting lower mean ADC values [11].

In contrast, germinomas are often more homogeneous in appearance, with relatively well-defined margins and uniform contrast enhancement. They may demonstrate intermediate diffusion restriction, with ADC values typically higher than those of pineoblastomas but lower than normal brain parenchyma [11]. Nevertheless, substantial overlap exists, and imaging findings alone remain insufficiently specific for definitive diagnosis [[10], [11], [12]]. In the present case, the bifocal distribution and homogeneous enhancement strongly suggested germinoma, whereas the marked diffusion restriction represented a subtle imaging feature that could have raised suspicion for a highly cellular embryonal tumor.

Accurate diagnosis is critical, as therapeutic strategies and prognoses differ substantially. Germinomas are highly radiosensitive and chemosensitive, with excellent long-term survival rates using relatively conservative treatment protocols [17]. In contrast, pineoblastomas require aggressive multimodal therapy, including maximal safe resection when feasible, craniospinal irradiation, and intensive chemotherapy, yet outcomes remain poor [1,2]. Misdiagnosis may therefore result in inadequate treatment of a highly malignant tumor.

In the present case, the suprasellar lesion may hypothetically represent metastatic seeding from the pineal tumor, given its smaller size and the known propensity of pineoblastomas for CSF dissemination [1]. The anterior recess of the third ventricle is a recognized site of metastatic implantation [18]. Although rare cases of primary suprasellar pineoblastoma have been reported [19], synchronous independent tumor development at both sites appears less probable.

Hydrocephalus management represents an additional challenge in such cases. While endoscopic third ventriculostomy can provide effective relief, its durability may be limited in rapidly proliferative tumors involving the suprasellar region [20]. In retrospect, ventriculoperitoneal shunting might have offered more reliable long-term cerebrospinal fluid diversion. This observation highlights the need to individualize CSF diversion strategies based on both anatomical considerations and tumor biology.

Conclusion

This case underscores the limitations of MRI in distinguishing bifocal germinoma from other malignant pineal region tumors. Although synchronous pineal and suprasellar lesions are classically associated with germinoma, rare entities such as pineoblastoma may present with an identical radiological pattern. Histopathological confirmation should therefore be strongly considered to ensure accurate diagnosis and appropriate treatment planning.

Patient consent

Written informed consent was obtained from the patient’s parents for the publication of this study and accompanying images.