Case contributed by Antonio Rodrigues de Aguiar Neto


A child with headache, vomiting, difficulty walking, and loss of equilibrium.

Patient Data

Age: 6 years
Gender: Male

Axial nonenhanced CT image shows a solid expansive heterogeneous midline posterior fossa mass with calcification and compressive effects on the fourth ventricle with consequent supratentorial hydrocephalus. There is periventricular hypodensity, suggesting transependymal CSF permeation. 

Impression: medulloblastoma is the primary diagnostic consideration.


MRI reveals the midline cerebellar mass, filling the fourth ventricle and compressing the brainstem and cerebellum. The tumor has a low signal on the T1 WI sequence compared with the surrounding normal cerebellum, mild hyperintensity on T2 WI, heterogeneous enhancement, cystic/necrotic component, and diffusion restriction, manifested by high B1000 and low ADC values, indicating high tumor cellularity. The lesion measures 4.2 x 4.4 x 5.7 cm, with discrete surrounding vasogenic edema. There are no intracranial or intraspinal CSF leptomeningeal metastases implants.  

Impression: The findings suggest medulloblastoma with no-CSF dissemination.


Post-surgical changes with craniotomy and bone flap replacement, accompanied by cerebrospinal fluid (CSF) content at the surgical opening with a thickness of up to 1.3 cm. Infra and supratentorial pneumocephalus. Ventricular shunt catheter.

Impression: The findings are consistent with post-surgical status in the posterior fossa.


Histopathological study report


The material received in formalin consists of five tissue segments, compact, irregular, elastic, white brown, the most extensive, measuring 3.5x 2.3x 1.3 cm.


The histological sections, serial and stained by HE, correspond to neoplasm malignant tumors of embryonic origin, consisting of small to medium-sized cells hyperchromatic nuclei arranged in a diffuse or nodular pattern. There is high mitotic activity and areas of necrosis.

Conclusion: Brain tumor resection product - posterior fossa - Medulloblastoma (grade 4, WHO) with nodular pattern areas.

Immunohistochemical study report

POSTERIOR FOSSA TUMOR: Hypercellular neoplasm consists of an atypical oval to polygonal cells, with hyperchromatic nuclei and scarce cytoplasm (photo 1). There are mitosis figures. The immunohistochemical study reveals positivity for synaptophysin (photo 2) and preservation of INI1 by the neoplasm. In this clinical and morphological context, the findings are consistent with MEDULOBLASTOMA GRADE 4 (WHO 2021). Immunohistochemical negativity for YAP1, filamin (most cells), and nuclear B-catenin, with marked nuclear positivity for OTX2 (photo 3), suggests the diagnosis of medulloblastoma non-WNT/non-SHH (WHO, 2021) from an Immunohistochemical point of view. However, due to limitations in this study, correlation with other additional molecular data is essential for diagnostic complementation and better molecular stratification.

Case Discussion

Medulloblastomas are a common pediatric malignant brain tumor divided into molecular subgroups with distinct characteristics (WHO 2021) – Wingless (WNT), Sonic hedgehog (SHH)-activated, Non-WNT/Non-SHH 1-4. This case illustrates histologically and Immunohistochemically proven medulloblastoma in the midline/fourth ventricle.

Case courtesy

  • Igor Faquine, MD - neurosurgeon
  • Auricélio Batista, MD – neurosurgeon
  • Mariana Lira, MD - pathologist
  • Antonio Rodrigues de Aguiar Neto, MD - radiologist


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