Tumors of Pineal Region

Non–germ cell tumors include pineal parenchymal tumors, glial tumors, and metastasis from systemic tumors. Pineal parenchymal tumors are traditionally classified as the lower-grade pineocytoma and the malignant pineoblastoma. Pineocytomas occur in middle-aged adults and are thought to be locally invasive. They are frequently managed with aggressive surgical resection and local radiotherapy for any residual tumor. Pineoblastomas resemble medulloblastomas histologically and predominate in the pediatric population. They are treated with multimodal therapy, which consists of maximal surgical resection followed by craniospinal irradiation and adjuvant chemotherapy, and they typically have a poor prognosis. Glial tumors may be low grade or high grade and are identical to glial neoplasms that occur elsewhere in the CNS. Because of their location, which is less accessible by surgery, they tend to have a poorer prognosis. Finally, cysts and meningiomas can also be found in the pineal region.

Clinical Manifestations. Clinical presentation of pineal region tumors include increased intracranial pressure from hydrocephalus, tectal dysfunction, and endocrinopathies. Obstruction of the third ventricle and cerebral aqueduct results in increased intracranial pressure, which manifests as headache, nausea, vomiting, lethargy, and papilledema. Because the lesions are located in the posterior aspect of the third ventricle, compression of the tectum often ensues. This can lead to Parinaud syndrome, which consists of vertical upward gaze paralysis, decreased or absent pupillary response to light, and convergence retraction nystagmus. Occasionally, cerebellar signs, such as ataxia and tremor, are seen with more extensive growth.

Diagnostic Studies. Neuroimaging is the first step in identifying a pineal region lesion. MRI with and without contrast is preferred because it outlines the tumor anatomy better than CT. Germinomas and pineal parenchymal tumors tend to have mixed T1 signal and increased T2 signal. Calcifications occur less frequently than in teratomas. Benign teratomas are well circumscribed and have mixed densities secondary to large cysts, areas of calcifications, and the occasional presence of teeth and hair. Although characteristic radiographic findings may be seen, they cannot substitute for histologic diagnosis.

Other studies include examination of tumor markers in the CSF. For mixed germ cell tumors, elevated alpha fetoprotein (AFP) levels confirm the presence of nongerminoma elements and high human chorionic gonadotropin (hCG) levels indicate a diagnosis of choriocarcinoma. The CSF should also be examined for the presence of malignant cells as a means to confirm the extent of disease, which can impact treatment planning.

Treatment. In general, surgery is almost always indicated for several reasons: establishment of a tissue diagnosis, symptomatic relief of hydrocephalus, and for therapeutic resection in anticipation of adjuvant treatment. For germinomas, extensive resection is not indicated; however, there is debate whether patients with nongerminomas benefit from radical surgery due to their decreased responsiveness to radiotherapy.

Radiation treatment is the standard treatment for pure germinomas. With radiation, long-term survival rates approximate 80% to 90%. However, this leads to genuine concerns for the potential delayed effects of therapy, such as neuroendocrine deficits, and neurocognitive deficits. Currently, there is much interest surrounding the use of chemotherapy in an effort to reduce the dose of irradiation used. Radiation is often combined with chemotherapy for treatment of nongerminomatous germinomas, which have a significantly poorer prognosis.

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