Pineal parenchymal tumour of intermediate differentiation

A 45-year-old female patient with history of headache and vomiting presented to the OPD. On examination, bulk, power and reflexes were normal. Initial laboratory results show no evidence of biochemical abnormalities and blood counts were normal. Then the patient was subjected to Imaging.

Magnetic resonance imaging (MRI) with contrast of the brain was performed in a 1.5 T Siemens Healthineers Magnetic resonance scanner, Erlangen Germany. MRI demonstrated a well-defined lesion which is T2 heterointense noted in the region of pineal gland. Fluid attenuated inversion recovery (FLAIR) images shows heterointense signal. On gadolinium administration, the lesion shows with enhancing solid areas and non-enhancing cystic areas. The ADC value of the tumour was 1.27 X 10^-3 mm2 s1.

The patient underwent a suboccipital craniectomy via an infratentorial supracerebellar approach and subtotal resection of pineal mass was done. Histopathological examination reveals diagnosis of pineal parenchymal tumour of intermediate differentiation (PPTID). The Patient was advised radiotherapy which the patient did not undergo. Review MRI of the brain after 10 months, with and without contrast was done which showed T2/FLAIR heterointense enhancing mass lesion in the pineal region suggestive of residual tumour.

Definition

Pineal parenchymal tumours arise from pineocytes (or their precursors) and are the second most common subgroup. Before 2007, only two subtypes of pineal parenchymal tumours were recognized by the World Health Organization (WHO) pineocytomas (WHO Grade I) and pineoblastomas (WHO Grade IV). In 2007, PPTID was established as a distinct entity to categorize a group of tumours that were between pineoblastomas and pineocytomas in histological grade[3]. Prior to the official WHO classification, tumours that fell in the spectrum between pineoblastomas and pineocytomas were described by various terms such as “atypical pineocytomas”, “malignant pineocytomas” or “mixed pineocytoma–pineoblastomas”[2]. It is now thought that many of these neoplasms were likely Pineal parenchymal tumour of intermediate differentiation.

Pineal parenchymal tumour of intermediate differentiation are lobulated, vascular pineal region masses that can extend into adjacent structures such as the ventricles or thalami.

Clinical presentation

The clinical presentation of a Pineal parenchymal tumour of intermediate differentiation is similar to that of other pineal region masses. Diplopia and headache are the most common symptoms. Parinaud’s syndrome (vertical gaze disturbance due to compression of the tectal plate) is another common finding. If large enough, Pineal parenchymal tumour of intermediate differentiation can cause hydrocephalus, leading to associated symptoms of elevated intracranial pressure such as ataxia.

Imaging key findings

Owing to high cellularity, Pineal parenchymal tumour of intermediate differentiation are usually hyperdense on CT scans and can demonstrate peripheral exploded calcifications. On MRI, these tumours are heterogeneously hypointense on T1 weighted and heterogeneously hyperintense on T2 weighted images. Cystic areas can be seen within the tumour as well. Heterogeneous enhancement is typical. Hydrocephalus is often seen owing to mass effect on the tectum.

Histologically, Pineal parenchymal tumour of intermediate differentiation appear as diffuse sheets of small uniform cells and are characterized by moderate-to-high cellularity, mild-to-moderate nuclear atypia and low-to-moderate mitotic activity. Absence of pineocytomatous rosettes should be noted[3]. On immunohistochemical staining, these neoplasms are strongly positive for synaptophysin and neuron-specific enolase with variable positivity for neurofilament protein, chromogranin A, retinal S-antigen, S-100 protein and B-tubulin[4].

Take-home message

Pineal parenchymal tumour of intermediate differentiation, although a rare tumour with no specific age predilection, has to be considered in the differential diagnosis of pineal region tumours in all age groups. These tumours may have a slight female predilection as in our case and are locally invasive with less likelihood of spinal or subarachnoid seeding.