Definition
- Essential:
- Demonstration of pineal parenchymal differentiation by histopathological and immunophenotypic features (e g. positivity for synaptophysin) AND
- Uniform cells forming large pineocytomatous rosettes and/or
- of pleomorphic cells showing gangliocytic differentiation
- Absence of criteria qualifying for the diagnosis of pineal parenchymal tumour of intermediate differentiation or pineoblastoma AND
- Low proliferative/mitotic activity AND
- Pineal region location
Numbers
- 14–30% of PPTs
- Mean age of diagnosis 43
- Male to female: 0.6:1
- < 1% of all intracranial neoplasms,
- 20% of all pineal parechymal tumours
- 27% of pineal region tumours are of pineal parenchymal origin
Localisation
- Pineal area
Cell origin
- Pinealocyte
- Derived from photoreceptor cells.
- A cell with photosensory and neuroendocrine functions.
- Regulation of melatonin synthesis → circadian rhythms
- Pineal gland and the retina share similar origin
CNS WHO grading
- Grade 1
Histopathology
Macroscopic
- Well circumscribed
- With cystic or haemorrhagic change sometimes evident.
- A grey or tan cut surface.
Microscopic
- Under light microscopy, pineocytomas are composed of small cells similar in appearance to normal pinealocytes, arranged in sheets;
- Pineocytomatous pseudorosettes
- Characteristic
- Not seen in normal pineal gland tissue
- Formed by tumour cells growing in sheets or lobules and collate around cytoplasmic processes
- Anucleate centres are composed of delicate, enmeshed cytoplasmic processes resembling neuropil
Immunophenotype
- Positive
- Synaptophysin
- Neurofilament
- Neurone-specific enolase
- Photosensory differentiation (retinal S-antigen and rhodopsin
- Interstitial cells can show positivity to glial markers (e.g. GFAP)
- Negative
- NeuN
- Variable
- Other neuronal markers (e.g. MAPT, chromogranin-A, 5-HT etc..)
- Ki-67 proliferation index is < 1%
Genetic profile
- No syndromic associations or genetic susceptibilities
Clinical presentation
- Compression of pineal s(x)
- Cerebral aqueduct:
- Obstruction HCP
- Papilledema
- H/A
- Ataxia
- Impaired vision
- N/V
- Brain stem
- Tectal plate compression: Parinaud syndrome
- Loss of upward gaze
- Cerebellum
- Dizziness
- Tremor
- Endocrine
- Diabetes insipidus
- Present with DI because it infiltrates the floor of 3rd ventricle affecting the pituitary
- Precocious puberty
- Acute clinical presentation can be due to tumour apoplectic
Radiological
General
- Slow growing and well-circumscribed tumours (compared to pineoblastomas that tend to be larger, and less well-circumscribed).
- When the cystic component is large, distinguishing them from pineal cysts can be difficult
- As is the case with the rest of the pineal gland, pineocytomas do not have a well-formed blood brain barrier and as such enhance vividly with contrast.
CT
- CT demonstrates the mass to be of intermediate density, similar to the adjacent brain.
- Pineal calcifications tend to be dispersed peripherally.
- This is the same pattern seen in other pineal parenchymal tumours, which is helpful in distinguishing these tumours from pineal germinomas that tend to 'engulf' pineal calcification.
MRI
- Solid components are isointense to brain parenchyma
- Areas of cystic change are common
- Sometimes the majority of the tumour is cystic
Management
Conservative:
- Radiological monitoring
- Indicated for Histologically confirmed small tumours (<1 cm)
- Because Pineocytoma grow slowly and morbidity of surgical resection is high.
Surgery
- Complete resection is curative and should be considered for symptomatic tumours.
- 5 yrs survival (Clark et al. 2010)
- 84% For gross total resection
- 17% subtotal resection and radiotherapy
Radiotherapy
- Indicated for residual tumour
- Radiotherapy has not shown to influence OS/PFS
Stereotactic radiosurgery
- Indicated
- As primary treatment for symptomatic tumour
- As primary therapy PFS rates are more than 85% after 30 months follow-up
- Studies reporting long-term outcomes are lacking and up to 50% of tumours show no growth which may simply reflect the natural history of small pineocytomas.
- Residual tumour after surgery
- Its efficacy may be higher for residual tumours and a 100% 5-year PFS has been reported in this context
Chemotherapy
- Not effective for newly diagnosed or recurrent pineocytoma
Prognosis
- Well- circumscribed tumours that grow slowly without disseminating through the CSF
- Good prognostic factor
- Gross total resection
Differential diagnosis
- Pineal cyst
- At most thin smooth (<2 mm) peripheral enhancement
- Have normal pineal parenchyma
- Normal pineal parenchyma does not show pineocytomatous rosettes.
- Other pineal parenchymal tumours
- Pineal parenchymal tumour with intermediate differentiation
- Pineocytoma does not show KBTBD4 alterations
- Pineoblastoma: larger, poorly defined
- Papillary tumour of the pineal region
- Germ cell tumours
- Germinoma
- Marked male predominance
- Engulfed calcification
- Embryonal carcinoma
- Choriocarcinoma
- Teratoma: may contain fat
- Astrocytoma of the pineal gland
- Metastasis
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