Pineal parenchymal tumours of intermediate differentiation (PPTID) are, as the name suggests, tumours that fall between pineocytoma (well-differentiated, WHO grade 1) and pineoblastomas (poorly differentiated, WHO grade 4). They are considered WHO grade 2 or 3 tumours 4. Their radiographic appearance and biological behaviour are also intermediate.
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Epidemiology
Although these tumours are encountered at all ages, they are particularly seen in middle-aged adults (20-70 years of age) with slight female predilection, similar to that of pineocytomas 4.
Pathology
Macroscopic appearance
Pineal parenchymal tumours with intermediate differentiation have a similar macroscopic appearance to pineocytomas, appearing relatively well-circumscribed with heterogeneous cut surface 4.
Microscopic appearance
Two microscopic patterns are encountered, sometimes co-existing 4:
- lobulated
- diffuse
In the lobulated pattern, poorly defined lobules are separated from each other by large fibrous vessels 4.
The diffuse pattern, on the other hand, is reminiscent of oligodendrogliomas and/or central neurocytomas, with the large pineocytomatous rosettes characteristic of pineocytomas not being evident 4.
Immunophenotype
- synaptophysin: positive 4
- NFP: variable
- NeuN: negative
Radiographic features
The features of pineal parenchymal tumours with intermediate differentiation range from those of pineocytomas to those of pineoblastomas, and they are therefore not repeated here.
When faced with a well-circumscribed pineal tumour with appearances of a pineocytoma, fairly rapid growth and/or low ADC values are clues that it may, in fact, represents a pineal parenchymal tumour with intermediate differentiation.
As these tumours may invade adjacent structures and also spread along CSF and therefore imaging of the entire craniospinal axis is therefore required 3.
Treatment and prognosis
Like everything else about this tumour, treatment and prognosis are intermediate falling between that of pineocytomas and of pineoblastomas.
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