Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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November 11, 2021
Papillary Tumor of the Pineal Region (PTPR)
- Background:
- PTPR is a rare neuroepithelial tumor that arises from specialized ependymocites in the subcommissural organ, located in the posteroinferior wall of the third ventricle (pineal region).
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Recognized neoplasm in the WHO 2007 classification; grading criterion has yet to be defined, but in the 2016 WHO, PTPR corresponds to grade II or III neoplasms.
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Only a few PTPRs with imaging findings have been reported.
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The immunohistochemical findings help differentiate PTPR from other lesions in the pineal region, such as pineal parenchymal tumor of intermediate differentiation (PPTID).
- Clinical Presentation:
- PTPR occurs in both children and adults, but most cases are seen in adults (mean age at diagnosis is 32 years).
- PTPR can compress the tectum and cerebral aqueduct, causing hydrocephalus.
- Key Diagnostic Features:
- PTPRs tend to be large and lobulated, relatively not well circumscribed, and partially cystic.
- MRI: T1WI variable signal intensity (intrinsic hyperintensity has been described); T2WI isointense or hyperintense and heterogeneous postcontrast enhancement; restricted diffusion on DWI
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In such scenarios, it is necessary to screen the entire neuraxis to assess for CSF spread.
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Radiologic findings are nonspecific in most patients. PTPRs are easily differentiated microscopically, showing distinct papillary architecture with pseudostratified columnar epithelium.
- Differential Diagnoses:
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PPTID: No radiologic features that would distinguish these tumors
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Pineocytoma: Well-demarcated round or nodular masses; the imaging appearance is less “aggressive” than a PTPR. MRI: Iso-hypointense on T1WI, hyperintense on T2WI, and variable enhancement
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Metastasis: Metastases to the pineal gland are rare (prevalence of 0.4%–3.8%), but may be present without metastases to brain parenchyma. Can be indistinguishable on imaging studies from primary pineal neoplasms.
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Germinoma: More than 90% of patients are younger than 20 years at initial diagnosis. MRI: Iso-hyperintense on T2WI, with intense and homogeneous enhancement. Dissemination by CSF and invasion of the adjacent brain are also typical.
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Brainstem astrocytoma with extension to the pineal region: Those that take place in the region of the tectum are usually low grade (WHO I–II) and occur more frequently in childhood. MRI: Bulbous enlargement of the tectal plate; isointense on T1WI and hyperintense on T2WI with no to minimal enhancement.
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Treatment:
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Surgical resection if it is possible
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The clinical course of PTPR is characterized by frequent local recurrence.
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The value of radiotherapy on disease progression in PTPR will need to be investigated in a future prospective trial, which will also provide data on long-term follow-up and may further aid the identification of histopathologic factors possibly associated with prognosis in PTPR.
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