Intraventricular Trigone Pleomorphic Xanthoastrocytoma: A Rare Presentation with Favorable Prognosis in a Young Adult—A Case Report

Abstract

Pleomorphic xanthoastrocytoma (PXA) is a rare, Grade II astrocytic tumor typically found in the temporal lobe and often presents with seizures. We report a unique case of intraventricular trigone PXA, a rare location that mimicked an intraventricular meningioma on imaging. A 26-year-old male presented with progressive visual loss, and magnetic resonance imaging revealed a well-defined lesion in the right lateral ventricle. The patient underwent subtotal tumor resection, followed by adjuvant radiotherapy. Histopathological analysis confirmed PXA with BRAF V600E mutation, and subsequent imaging showed successful tumor control with no recurrence after 2 years. This case highlights the importance of differentiating PXA from other neoplasms, such as meningiomas, and demonstrates the favorable prognosis of PXA when appropriately managed.

Keywords

pleomorphic xanthoastrocytoma - intraventricular trigone - gliomas

Introduction

Pleomorphic xanthoastrocytoma (PXA) is a rare astrocytic tumor, accounting for approximately 1% of all astrocytic tumors.[1] It is classified as a Grade II tumor according to the World Health Organization (WHO) classification.[2] PXAs are typically supratentorial tumors, with the temporal lobe being the most common location, followed by the frontal and parietal lobes. They are characteristically superficial, cortical-based tumors, and as a result, longstanding epilepsy is the most frequent clinical presentation.[3]

Although PXAs most commonly occur in the supratentorial region, rare cases have been reported in the suprasellar region, pineal region, cerebellum, and spine.[4] [5] [6] [7] On magnetic resonance imaging (MRI), PXAs often exhibit both cystic and solid components. The cystic component appears hypointense on T1-weighted images (T1-WI) and hyperintense on T2-weighted images (T2-WI), whereas the solid component, including mural nodules or thick cyst walls, appears hypointense or isointense on T1-WI and slightly hyperintense on T2-WI. After gadolinium administration, there is typically marked enhancement of the solid component and peripheral rim enhancement of the cyst.[3] We report a rare case of intraventricular trigone solid PXA, which closely mimicked an intraventricular meningioma on imaging. The patient underwent subtotal tumor resection followed by adjuvant radiotherapy, resulting in successful tumor control.

Case History

A 26-year-old Thai male with no known medical history presented with progressive bilateral visual loss over a period of 3 months. On physical examination, he was alert, cooperative, and exhibited preserved interaction and visual acuity, but was found to have right homonymous hemianopia.

MRI of the brain revealed a well-defined lesion located at the right trigone of the lateral ventricle. On T1-WI, the lesion appeared hypointense relative to the surrounding brain tissue. T2-W1 demonstrated a hyperintense signal with surrounding vasogenic edema extending into the adjacent white matter. Similarly, on fluid-attenuated inversion recovery imaging, the lesion remained hyperintense, with significant perilesional edema, suggesting an impact on adjacent brain structures. Post-contrast T1-W1 revealed a 5.5 × 3.7 × 5.4 cm lesion with homogeneous contrast enhancement, indicating a vascularized tumor with a well-defined margin within the trigone and temporal horn of the right lateral ventricle, without evidence of intralesional necrosis or cystic degeneration ([Fig. 1]).

Fig. 1 (A) T1-weighted imaging, (B) T2-weighted imaging, (C) FLAIR imaging, and (D) post-contrast T1-weighted imaging in axial, sagittal, and coronal views. FLAIR, fluid-attenuated inversion recovery imaging.

The patient subsequently underwent a right occipital craniotomy with an occipital corticotomy to expose the posterior horn of the lateral ventricle. Upon opening the ependymal layer of the left lateral ventricle, a vascularized, encapsulated, soft, and suckable grayish tumor was identified, suspected to have originated from the left temporal base periventricular area, at the interface between the occipital horn and the ventricle ([Fig. 2]). The tumor was carefully debulked internally, and tissue samples were sent for pathological examination. Following extracapsular dissection and tumor resection, the patient regained normal consciousness postoperatively. However, he continued to experience stable visual loss with persistent right homonymous hemianopia, without evidence of obstructive hydrocephalus.

Fig. 2 Microscopic view during occipital corticotomy, exposing the trigone of the lateral ventricle.

The tumor was sent for pathological examination. On gross examination, the specimen consisted of multiple irregular pieces of rubbery gray and brown tissue. The cut surface also showed rubbery gray and brown tissue ([Fig. 3]). Microscopic examination revealed a spindle cell tumor arranged in a fascicular pattern, with a few epithelioid cells displaying pleomorphic nuclei interspersed within the spindle cells. No mitotic figures or brain invasion was noted. A small area of necrotic tissue was identified. There was no evidence of meningioma or mesenchymal tumor ([Fig. 4]).

Fig. 3 Gross examination revealed several irregular fragments of rubbery, gray, and brown tissue. The cut surface also displayed similar rubbery, gray, and brown tissue.

Fig. 4 H&E pathology review. Upper image: tumor with a fascicular growth pattern, showing bundles of tumor cells. Lower image: epithelioid cells with pleomorphic nuclei, indicating cellular heterogeneity and potential malignancy.

To further characterize the tumor, the pathologist requested immunohistochemical (IHC) staining for Somatostatin receptor 2A (SSTR2A), epithelial membrane antigen (EMA), Progesterone receptor (PR), desmin, smooth muscle actin (SMA), Cytokeratin 7 (CK7), Cytokeratin 20 (CK20), glial fibrillary acidic protein (GFAP), synaptophysin, and transthyretin. The IHC results were as follows: GFAP and synaptophysin were positive, while CK7, CK20, EMA, SSTR2A, PR, and desmin were negative. SMA showed scattered positivity ([Fig. 5]), and transthyretin was positive.

Fig. 5 Immunohistochemistry for SMA. Positive staining for SMA, confirming smooth muscle differentiation. SMA, smooth muscle actin.

Based on these findings, the provisional diagnosis was a neuroepithelial tumor, with differential diagnoses including pleomorphic astrocytoma (excluding ependymoma and oligodendroglioma) or a glioneuronal tumor. To refine the diagnosis, additional IHC studies were performed, including neurofilament protein (NFP), ATRX, Olig2, p53, IDH1, K_i-67, and special stains for reticulin. A molecular study for BRAF mutation and CD34 was also suggested.

The additional IHC results revealed that Olig2 was expressed in many tumor cells, with no loss of ATRX expression. IDH1 R132H was nonreactive, and p53 was expressed in rare tumor cells. NFP highlighted rare nerve fibers, while CD34 primarily marked blood vessels. The K_i-67 index was approximately 5 to 10%, indicating a moderate proliferation rate. The BRAF V600E mutation test confirmed the presence of a mutation. With these findings, the final diagnosis was BRAF V600E-mutant neuroepithelial tumor, with morphology most consistent with PXA, WHO Grade 2.

A follow-up MRI at 3 month post-surgery revealed a 1 cm residual homogeneously enhancing mass at the temporal base, near the occipital horn, suspected to be residual tumor. The patient subsequently received adjuvant radiotherapy, administered at 2 Gy per day for 28 days. Despite treatment, he continued to experience persistent right homonymous hemianopia.

At the 2-year follow-up, MRI revealed a decrease in the size of the homogeneously enhancing lesion at the right trigone of the lateral ventricle ([Fig. 6]), with no evidence of tumor recurrence, indicating successful tumor control.

Fig. 6 Postoperative MRI brain (3 months). T1-weighted imaging with gadolinium. (A) Axial view, (B) sagittal view, and (C) coronal view. MRI, magnetic resonance imaging.

Discussion

PXA is a rare astrocytic tumor that predominantly affects children and young adults and often presents with seizures due to its frequent temporal lobe involvement.[1] Imaging typically reveals a well-circumscribed cortical mass with cystic components and vivid contrast enhancement; however, atypical features, such as homogeneous enhancement and perilesional edema, can mimic meningiomas.[8] Histologically, PXA is characterized by pleomorphic, spindle-shaped, and multinucleated giant cells with abundant reticulin deposition, whereas meningiomas display uniform spindle cells arranged in whorls with psammoma bodies.[9]

In the diagnostic evaluation of PXA, a comprehensive IHC panel is essential to accurately characterize the tumor and differentiate it from other neoplasms. Initial histological examination typically reveals pleomorphic, spindle-shaped, and multinucleated giant cells with a rich reticulin network. To confirm the astrocytic origin, IHC staining for GFAP is performed, as PXAs usually express GFAP. Additionally, S100 protein is often diffusely positive in these tumors.[10]

Given the frequent occurrence of BRAF V600E mutations in PXAs, testing for this mutation is crucial, as it can aid in diagnosis and potentially guide targeted therapy.[10] [11] Furthermore, assessing the proliferation index through K_i-67 labeling provides insight into the tumor's growth potential.[12] To exclude other entities in the differential diagnosis, such as meningiomas or other gliomas, additional IHC markers may be employed. For instance, EMA is typically positive in meningiomas but negative in PXAs. In challenging cases, molecular studies, including CDKN2A/B deletion analysis, can provide further diagnostic clarity, as these deletions are frequently observed in PXAs.[13]

Prognostically, PXAs generally have a favorable outcome, but up to 35% of cases may experience recurrence or malignant transformation, especially in cases with residual tumor post-surgery.[9] [14] In the presented case, the patient's residual tumor was effectively managed with adjuvant radiotherapy, leading to no recurrence over a 2-year follow-up, which aligns with successful tumor control reported in similar cases.

Conclusion

PXA is a rare and typically favorable tumor, though its atypical presentations, such as intraventricular location, may challenge diagnosis. Accurate identification through advanced imaging, histopathology, and immunohistochemistry is essential to distinguish PXA from other neoplasms, including meningiomas. The frequent BRAF V600E mutation highlights the importance of molecular testing for diagnosis and potential targeted therapy. While PXAs generally have a good prognosis, vigilant monitoring for recurrence is necessary, particularly in cases with residual tumor. This case underscores the value of comprehensive diagnostic approaches and adjuvant treatments in achieving successful long-term outcomes.

Conflict of Interest

None declared.

Acknowledgments

The author sincerely appreciates Dr. Shanop Shuangshoti from the Department of Pathology, Faculty of Medicine, Chulalongkorn University, and King Chulalongkorn Memorial Hospital, Bangkok, Thailand, for his expertise in pathology and his invaluable contributions to the management, analysis, and precise pathological diagnosis of this case.

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Publikationsverlauf

Artikel online veröffentlicht:
01. Mai 2025