Papillary tumour of the pineal region
Papillary tumours of the pineal region (PTPR) are a relatively recently described entity, and considered one of four pineal parenchymal tumours under the current (2016) WHO classification of CNS tumours.
Papillary tumour of the pineal region are seen in a wide range of ages, reported from 1-70 years of age, with most cases found in middle age 3,4. They are encountered equally in both genders 3.
As with all other pineal region masses clinical presentation is mainly from obstructive hydrocephalus secondary to compression of the tectum of the midbrain and obstruction of the aqueduct. Compression of the superior colliculi can also lead to a characteristic gaze palsy, known as Parinaud syndrome.
Papillary tumour of the pineal region are though to arise from specialised ependymocytes of the subcommissural organ located in the lining of the posterior commissure rather than from the pineal gland itself 1-3. It is also hypothesised that some, or perhaps many, previously published descriptions of unusual pineal region tumours (e.g. choroid plexus papillomas and papillary ependymomas) actually represent PTPRs, as histologically they are difficult to distinguish, requiring immunohistochemistry 1.
These tumours are considered WHO grade II or III tumours 3.
Papillary tumour of the pineal region are macroscopically indistinguishable from pineocytomas, appearing as well circumscribed tumours of the pineal region 3.
Papillary tumour of the pineal region demonstrate varible morphology ranging from solid to predominantly papillary, reminiscent of ependymomas, including the presence of ependymal rosettes 3. Areas of necrosis are sometimes identified 3,4.
PTPRs have a fairly characteristic immunohistochemical profile that allows them to be distinguished from other pineal parenchymal tumours.
- cytokeratins (AE1/3, CAM5.2, KL1, CK18): positive
- S100: positive
- vimentin: positive
- tansthyretin: positive
- neuron-specific enolase: positive
- MAP2: positive
- GFAP: variable
Papillary tumours of the pineal region are often indistinguishable from pineocytomas. Sometimes they demonstrate intrinsic high T1 signal attributed to secretory inclusions 1,3. This is a relatively specific findings when other causes of T1 shortening are excluded (e.g fat in a teratoma or lipoma, melanoma, haemorrhagic metastases) 1,3.
Screening of the entire neural axis is required as CSF dissemination has been reported in up to 7% of cases 4.
On imaging consider other pineal region masses, particularly:
- pineocytoma and pineal parenchymal tumour of intermediate differentiation: indistinguishable from each other based only on imaging and immunohistochemistry tests are required
- 1. Chang A.H., G.N. Fuller, J.M. Debnam et al. “MR Imaging of Papillary Tumor of the Pineal Region.” AJNR Am J Neuroradiol 29, no. 1 (January 1, 2008): 187-189. doi:10.3174/ajnr.A0784.
- 2. Jouvet Anne, François Fauchon, Pawel Liberski et al. “Papillary Tumor of the Pineal Region.” The American Journal of Surgical Pathology 27, no. 4 (2003). [Link].
- 3. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK "WHO Classification of Tumours of the Central Nervous System. 4th Edition Revised" ISBN: 9789283244929
- 4. Dumrongpisutikul N, Intrapiromkul J, Yousem DM. Distinguishing between germinomas and pineal cell tumors on MR imaging. AJNR Am J Neuroradiol. 2012;33 (3): 550-5. AJNR Am J Neuroradiol (full text) - doi:10.3174/ajnr.A2806 - Pubmed citation
Pineal region masses
The pineal region is anatomically complex and plays host to a number of unique masses and tumours as well as potentially affected by many entities seen more frequently elsewhere in the brain.
- cystic non-neoplastic lesions
- pineal parenchymal tumours
- germ cell tumours
- tumours also encountered in the pineal region
- pineal gland metastases
- vascular lesions