Pineocytoma is a pineal cell tumor (AKA pinealcytoma) is a well dfferentiated neoplasm arising from pineal epithelium. Pineoblastoma (AKA pinealblastoma) is a malignant tumor that is considered a primitive neuroectodermal tumor (PNET). Both can metastasize through the CSF, and both are radiosensitive.
Pineocytomas are pineal parenchymal tumour, are generally non-agressive and have a relatively good prognosis.
Pineocytomas can be encountered at any age but mostly occur in young adults in the second decade of life
Unlike pineal germinomas both genders are equally affected.
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.
Pineocytomas are well differentiated tumours, and considered a WHO grade I tumours (or sometimes grade II lesions - depending on the source - see WHO classification of CNS tumours). 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
Under light microscopy, pineocytomatous pseudorosettes are characteristic.
Typically pineocytomas are slow growing and well circumscribed (compared to pineoblastomas which tend to be larger, and less well circumscribed) tumours. They tend to be solid, although focal areas of cystic change, or haemorrhage do occur. When the a cystic component is large distinguishing them form pineal cysts can be difficult although it has been postulated that this is not so much the case is complete and thorough imaging is obtained (i.e. good quality thin section MRI with contrast).
CT
CT demonstrates the mass to be of intermediate density, similar to adjacent brain. Pineal calcifications tend to be dispersed peripherally. This is the same pattern as is seen in other pineal parenchymal tumours but is helpful in distinguishing these tumours from pineal germinomas which then to 'engulf' pineal calcification.
MRI
MRI is the modality of choice for examining tumours of the pineal region.
T1: isointense to brain parenchyma
T2 solid components are isointense to brain parenchyma areas of cystic change are common sometimes the majority of the tumour is cystic T1 C+ (Gd): solid components vividly enhance Treatment and prognosis
Pineocytomas are treated surgically and have an excellent prognosis when a complete resection is achieved (which is most of the time as they are well circumscribed lesions). A 5 year survival of 86% has been reported.
Local recurrent and even CSF metastases are reported but rare.
Differential diagnosis
On CT or MRI consider:
pineal cyst at most thin smooth (<2 mm) peripheral enhancement other pineal parenchymal tumours pineal parenchymal tumour with intermediate differentiation 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 pineal gland metastasis
A 58-year-old male with an unsteady gait for 2 months. Enhanced brain magnetic resonance imaging revealed a heterogeneous mass involving the pineal region. The initial pathological diagnosis of pineocytoma was confirmed after subtotal tumor resection. Two years after adjuvant radiotherapy to the primary site, the magnetic resonance imaging showed C2 and T2 metastatic lesions, with the final pathological diagnosis being pineal parenchymal tumor (PPT) with intermediate differentiation after the removal of T2 intramedullary tumor. After that adjuvant radiotherapy at the cervical and thoracic spinal cord was completed. There was no recurrence of the tumor 1 year after the radiotherapy. We report a rare case of pineocytoma with malignant transformation to PPT with intermediate differentiation and leptomeningeal dissemination 1).