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Pineoblastoma

Leyla Azmoun, MD
Amir Zamani, MD

July 27, 1994

Presentation

A 41-year-old man presented with headache and seizures.

Imaging Findings

T1 weighted MRI
T2 weighted MRI
Post-gadolinium MRI

MRI of the brain shows a 4.5 x 3.5 cm soft tissue mass in the pineal region. The mass appears slightly hypointense to parenchyma on T1-weighted images (Image 1, with arrow) and isointense to grey matter on T2-weighted images (Images 2 and 3, with arrows). There is relatively homogeneous enhancement of the mass following contrast administration with a central focal area of hypointensity (Images 4 and 5, arrows), most likely representing cystic necrosis. The mass (arrows) extends superiorly into the splenium of the corpus callosum (short black arrow), anteriorly into the quadrigeminal plate in the midbrain (short white arrow), and inferiorly into the vermis of the cerebellum (long white arrow).

Differential Diagnosis

Common pineal region tumors include pineal cell tumors (pineocytoma and pineoblastoma), germ cell tumors (germinoma, choriocarcinoma, and teratoma), gliomas, and meningiomas. MRI signal characteristics are usually nonspecific for differentiating between these tumors. However, the large size of this mass (greater than 4 cm) and its irregular shape suggest pineoblastoma or malignant teratoma. Based on the patient's age and sex as well as imaging characteristics of the mass, pineoblastoma is the more likely possibility.

Diagnosis

Pineoblastoma

Discussion

Pineoblastomas are highly malignant neoplasms which arise from pineoblasts, the primitive pineal stem cells. These tumors occur at any age and are slightly more common in males (M:F 1-4:1). They are invasive tumors that tend to metastasize in the cerebrospinal fluid (CSF) spaces.

MRI depicts these masses as large, lobulated, generally solid tumors with areas of cystic necrosis. The signal characteristics vary, but in general pineoblastomas are essentially isointense to grey matter on both T1 and T2-weighted images. The tumors enhance homogeneously with contrast. These signal characteristics are seen in other primitive neuroectodermal tumors (PNET) and are probably related to scant cytoplasm and overall dense cellularity of these tumors. The prognosis for patients with pineoblastomas is generally poor.

References

1. Tien R, Barkovich A, Edwards M. MR imaging of pineal tumors. AJNR May 1990:557-565.

2. Atlas S. Magnetic resonance imaging of the brain and spine. 1st ed. New York, Raven Press, 1991:296-298.

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