Pineal parenchymal tumor with intermediate differentiation

Magnetic

resonance imaging of pineal region tumours. Pineal parenchymal tumour of indeterminate differentiation (PPTID) in a 33-year-old woman with blurry vision and headaches. A circumscribed lesion with well- defined margins is seen involving the pineal gland (arrow), which has mixed intermediate and high signal on axial (a) and sagittal (b) T2-weighted images. The tumour shows heterogeneous contrast enhancement on sagittal T1-weighted image (c)

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Pineal parenchymal tumors with intermediate differentiation (PPTID) are, as the name suggests, tumors which fall between pineocytoma (well differentiated, WHO grade I) and pineoblastomas (poorly differentiated, WHO grade IV). They are considered WHO grade II or III tumors . Although these tumors are encountered at all ages, they are particularly seen in middle age adults (20-70 years of age) with slight female predilection, similar to that of pineocytomas .

Their radiographic appearance and biological behavior are also intermediate. They may invade adjacent structures and also spread along CSF and therefore imaging of the entire craniospinal axis is therefore required .

Pathology

Macroscopic appearance

Pineal parenchymal tumors with intermediate differentiation have a similar macroscopic appearance to pineocytomas, appearing relatively well circumscribed with heterogeneous cut surface .

Microscopic appearance

Two microscopic patterns are encountered, sometimes co-existing :

lobulated

diffuse

The lobulated pattern, poorly defined lobules are separated from each other by large fibrous vessels .

The diffuse pattern is reminiscent of oligodendrogliomas and/or central neurocytomas, with the large pineocytomatous rosettes characteristic of pineocytomas not evident .

Immunophenotype

synaptophysin: positive
NFP: variable
NeuN: negative

Radiographic features

The features of pineal parenchymal tumor 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 tumor with appearances of a pineocytoma, fairly rapid growth and/or low ADC values are clues that it may, in fact, represents a pineal parenchymal tumor with intermediate differentiation.