Pineal region tumours

General characteristics

The most common tumours in this area are teratomas or germinomas. Pineocytomas are less common and arise from the pineal parenchymal cells, and gliomas can also arise in the pineal region.

Aetiology

Pineal region tumours can arise from a number of cell types.

Epidemiology

Occasionally metastases can spread to the pineal region. In addition to these solid tumours, pineal region cysts can occur and can be simple, filled with CSF, or can be epidermoid or dermoid cysts.

Pineal region tumour:

  • pineal glioma,
  • ependymoma,
  • pineocytoma,
  • germinoma,
  • teratoma.

Diagnostics

If germ cell markers (α-fetoprotein (AFP) and β-human chorionic gonadotropin (β-hCG)) are positive, biopsy of the lesion is not required. Elevated germ cell markers indicate a malignant germ cell tumour. These patients can be treated with radiation therapy and chemotherapy, and can be followed by measuring the tumour markers. If the lesion enlarges but markers reduce, surgical debulking may be necessary (Lee et al. 1995). In the absence of tumour markers, surgical confirmation is strongly advised.

Imaging

Preoperative or 12-day postoperative spinal MR imaging may identify spinal seeding from the pineal region tumour.

Treatment

Hydrocephalus may have to be dealt with first, either by external drainage or placement of a ventriculo-peritoneal shunt. In the presence of mild hydrocephalus, some surgeons prefer performing a definitive resection and placing a ventricular drain at the time of surgery, which later can be clamped and removed, or changed into a ventriculo-peritoneal shunt. Other authors have suggested performing a third ventricular ventriculostomy (Goodman 1993).

If the frozen section reveals germinoma, then there is no need to proceed to resection because this tumour is so radiosensitive (control rates of 90 per cent) and chemosensitive.

If the biopsy confirms a benign pineal region tumour (dermoid, epidermoid, pilocytic astrocytoma, ependymoma, or pineocytoma) maximum resection should be attempted, and is generally the only treatment necessary.

If the biopsy demonstrates a malignant pineal region tumour (e.g. a non-germinomatous germ cell tumour, choriocarcinoma, embryonal cell carcinoma, immature teratoma or endodermal sinus tumour, malignant glioma), then maximum resection is probably advisable, especially if the patient is young and has a good performance status.

Complications of surgery include disorders of eye movement, ataxia, and cognitive problems. If a supratentorial approach to the tumour is taken, there is a higher incidence of visual field defects and hemiparesis. Surgical complications for pineal region tumours range up to 12 per cent and mortality up to 8 per cent (Bruce and Stein 1993).

Standard radiation schedules for germinoma consist of 4000 cGy to the whole brain and a boost to 5500 cGy to the pineal region. Radiation therapy dosages of less than 5000 cGy are associated with increased risk of recurrence (Schild et al., 1993).