A Rare Instance of Adult Medulloblastoma Presenting Imaging Heterogeneity Correlating With Molecular Subtypes and Anatomical Locations

ABSTRACT

We report an adult medulloblastoma presenting as two imaging‐distinct lesions: a uniformly enhancing torcular mass (WNT‐activated) and a non‐enhancing cerebellar tumor (SHH‐activated). A cohort analysis confirmed torcular location favors uniform enhancement, mimicking meningioma. Accurate diagnosis requires integrating molecular subtypes and location‐specific hemodynamics.

1. Introduction

Medulloblastoma is the most common malignant primitive neuroectodermal tumor, particularly prevalent in children and adolescents, and accounts for approximately 20% of primary intracranial tumors in this population. However, it accounts for only 0.4%–1% [1] of primary intracranial tumors in adults, with an even rarer incidence in patients over 60 years old. In adults, medulloblastomas are typically solitary [2]. This report presents a case of a 60‐year‐old female patient who was admitted for dizziness and unsteady gait. Imaging revealed two tumor lesions in the infratentorial region, exhibiting significant differences in their imaging characteristics. This case report analyzes an adult medulloblastoma and investigates how molecular subtypes and anatomical locations influence its imaging features by a literature review.

2. Case History

2.1. Case Presentation

A 60‐year‐old female patient presented with a 1‐month history of dizziness and unsteady gait. Then she developed non‐projectile vomiting and blurred vision. Neurological examination revealed impaired distance judgment, a positive finger‐to‐nose test, and a positive heel‐to‐shin test. MRI revealed an irregular mixed T1 signal in the left cerebellar hemisphere‐tonsil region without enhancement, measuring approximately 2.1 × 2.3 × 2.2 cm³, with compression and distortion of the fourth ventricle and pons, accompanied by significant surrounding edema (Figure 1C,D,F). A short T1 signal mass was observed in the left cerebellar torcular region, measuring approximately 2.5 × 2.7 × 2.3 cm³, with uniform enhancement (Figure 1A,B,E). Preoperative diagnoses considered medulloblastoma and meningioma.

FIGURE 1.

Magnetic resonance imaging findings during the patients' treatment: Enhanced MRI scan showing a left‐sided contrast lesion in the torcular region and cerebellar hemisphere, measuring 2.5 × 2.7 × 2.3 cm³ and 2.1 × 2.3 × 2.2 cm³ (A–D); Axial T2‐weighted images (E, F).

2.2. Methods

The patient underwent tumor resection, with the tumor in the torcular region exhibiting abundant blood supply, and the tumor base was deeply involved in the torcular region, whereas the cerebellar hemisphere lesion showed relatively minimal hemorrhage (Figure 2). Pathological examination confirmed medulloblastoma, WHO Grade IV. The tumor in the torcular region exhibits abundant spindle cells arranged in an interlacing fascicular pattern, accompanied by markedly hyperchromatic nuclei (Figure 3A). And the cerebellar tonsillar neoplasm is situated in close apposition to the adjacent normal brain parenchyma, demonstrating a striking disparity in cellular density (Figure 3B). The Ki‐67 labeling index of the tumor is approximately 40% (Figure 3C). Postoperatively, the patient had an uneventful recovery and was discharged from the hospital.

FIGURE 2.

Torcular tumor (A); Cerebellar hemisphere tumor (B).

FIGURE 3.

HE staining at low magnification (×100) showing high nuclear‐cytoplasmic ratio, abundant reticulin fibers, and nodular tumor formation: Torcular region (A) and cerebellar hemisphere (B). The Ki‐67 labeling index of the tumor is approximately 40% (C). The tumor located in the torcular region shows positive reticulin staining (×100) (D). Immunohistochemical staining for β‐catenin in the torcular lesion demonstrates diffuse and strong nuclear positivity in > 80% of tumor cells, consistent with a WNT‐activated molecular profile (E). Immunohistochemical staining for β‐catenin in the cerebellar hemisphere lesion shows negative nuclear immunoreactivity. Although membranous and cytoplasmic staining is present, no nuclear translocation is observed (F).

3. Discussion

Medulloblastoma is a malignant primitive neuroectodermal tumor that typically occurs in the cerebellum, most commonly in children and adolescents, with a considerably lower incidence in adults [3]. Medulloblastomas typically present with certain imaging features on conventional imaging (MRI, CT), such as low T1‐weighted imaging (T1WI) signals and high T2‐weighted imaging (T2WI) signals. These tumors are usually located in the cerebellum and fourth ventricle, often accompanied by surrounding edema [4]. On enhanced imaging, medulloblastomas typically show uneven enhancement. However, in some cases, the tumor may display necrosis, hemorrhage, or cystic degeneration, leading to more diverse imaging presentations [5]. The imaging differences observed in our patient prompt a reevaluation of the imaging characteristics of adult medulloblastoma. The cerebellar lesion exhibited mixed T1 signals with no enhancement, while the torcular lesion showed short T1 signals with uniform enhancement, suggesting that the imaging phenotype in medulloblastoma may be dictated by a combination of its molecular subtype and the anatomical microenvironment.

Medulloblastoma is classified into distinct molecular subtypes based on genetic features and clinical presentation, including WNT‐activated, SHH‐activated TP53 wildtype, SHH‐activated TP53‐mutant, and non‐WNT/non‐SHH subtypes [6]. These subtypes can influence the tumor's imaging characteristics and clinical behavior. WNT‐activated medulloblastomas are typically smaller, localized, with well‐defined borders, and often show uniform enhancement on contrast‐enhanced imaging. Consequently, they are generally associated with a more favorable prognosis [7]. In contrast, SHH‐activated medulloblastomas often present with multiple lesions and may invade the cerebellar hemisphere, pons, or spinal cord. This type of tumor may appear as large or multifocal lesions on imaging and typically has a worse prognosis. They may also exhibit more complex imaging features, such as irregular shapes and uneven enhancement [8]. The imaging characteristics of other medulloblastoma subtypes remain inconclusive. This patient's postoperative molecular analysis revealed distinct subtype profiles between the two lesions. Immunohistochemical staining for β‐catenin (Figure 3E,F) showed that the torcular lesion had diffuse and strong nuclear positivity in > 80% of tumor cells, consistent with the WNT‐activated subgroup, while the cerebellar hemisphere lesion demonstrated no nuclear immunoreactivity, with staining confined to the membrane and cytoplasm (Figure 3F). Furthermore, the cerebellar hemisphere lesion showed strong immunoreactivity for SHH pathway markers (SFRP1 and GAB1) with a high Ki‐67 index (> 40%), aligning with the SHH‐activated subgroup. Neither lesion exhibited MYC or MYCN amplification. These findings support the presence of intratumoral molecular heterogeneity, which correlates with the observed differences in imaging phenotypes.

Hemodynamically, the flow velocity in the torcular region is significantly lower than in other regions, with an average velocity of 2–5 cm/s. This slow blood flow may cause contrast agents to remain in the area for a longer period, leading to more pronounced enhancement on MRI [9]. Additionally, the torcular region, where the superior sagittal, straight, and bilateral transverse sinuses converge, experiences complex turbulence and changes in blood flow direction [10], with a significantly higher local venous pressure gradient compared to other regions [11]. The slow blood flow in the torcular region promotes the development of a more extensive vascular network in tumors, which may provide the structural basis for uniform enhancement [9]. This is further supported in our case by the positive reticulin stain, highlighting the prominent stromal and vascular network within the tumor (Figure 3D). Complex turbulent flow may induce changes in endothelial cell mechanical stress, which in turn could modulate the growth behavior of tumors [12]. The hemodynamic variations associated with anatomical location may play a significant role in the markedly different imaging appearances observed between the two lesions. This phenomenon thus poses a considerable challenge for accurate preoperative diagnosis.

To explore the association between location and enhancement pattern, we retrospectively analyzed data from 25 adult medulloblastoma patients (aged > 40 years) treated at our institution (2013–2025). Notably, among the 10 cases involving the torcular region, seven cases (70%) showed uniform enhancement, while only 2 of the 15 cases with solitary cerebellar hemisphere lesions showed uniform enhancement (13.3%) (χ ² = 6.20, p = 0.0128). Comprehensive pathological analysis results were not available for these patients. Preoperatively, we considered meningioma as a possible diagnosis for the lesion in the torcular region, as meningiomas often present as subdural or extradural masses with clear boundaries and typically show uniform enhancement on contrast‐enhanced imaging [13]. This can be confounded with the distinctive imaging features of torcular region tumors. In cases involving multiple brain tumors, particularly when imaging differences are significant, we recommend prioritizing tumor homogeneity and considering the possibility of multiple lesions of the same type, and noting the unique imaging characteristics of torcular region tumors.

4. Conclusion

This case of adult medulloblastoma demonstrates a direct correlation between profound intratumoral imaging heterogeneity, distinct molecular subtypes (WNT‐activated and SHH‐activated), and specific anatomical locations. The uniformly enhancing torcular lesion, likely influenced by local hemodynamics, can mimic meningioma and poses a significant diagnostic challenge. Our findings emphasize that accurate imaging interpretation in adult medulloblastoma requires an integrated assessment of molecular pathology and location‐specific microenvironmental factors.

Author Contributions

Zechen Wang: writing – review and editing, resources, formal analysis, supervision, data curation, software, project administration, visualization, validation, methodology, conceptualization, investigation, funding acquisition, writing – original draft. Chao Guan: writing – original draft, writing – review and editing. Jianing Zhang: writing – original draft, writing – review and editing. Jie Wu: writing – review and editing, writing – original draft. Yunqing Chen: writing – original draft, writing – review and editing. Yugong Feng: writing – original draft, writing – review and editing. Zhenwen Cui: writing – review and editing, writing – original draft. Chen Shen: writing – original draft, writing – review and editing. Pin Guo: writing – original draft, funding acquisition, investigation, conceptualization, methodology, validation, visualization, writing – review and editing, project administration, formal analysis, software, data curation, supervision, resources.

Funding

The authors have nothing to report.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

All data from this case is in the article and its figures. No extra datasets exist since it's a single case report.