Melanocytic lesions are diffuse or circumscribed, benign, or malignant tumors arising from melanocytes of the leptomeninges. They include diffuse melanocytosis (diffuse melanosis) and neurocutaneous melanosis, melanocytoma, and malignant melanoma. Intermediate or mixed cases may occur. Melanocytoma accounts for 0.06% to 0.1% of brain tumors; the other melanocytic lesions are rarer. These lesions typically occur in the fifth decade of life with a female to male ratio of 2:1. Diffuse melanocytosis involves the supratentorial and infratentorial leptomeninges; melanocytomas occur as solid masses in the cranial and spinal compartments. Diffuse melanocytosis and malignant melanoma both carry a poor prognosis.
(Refer to the Meningeal Tumors section of this summary for treatment information.)
Germ cell tumors
As a group, CNS germ cell tumors vary widely in their incidence. In Europe and North America, they comprise 0.3% to 0.5% of all primary brain tumors; in Asia, these types of tumors account for at least 2.0% of all primary brain tumors. Germ cell tumors are primarily neoplasms of the young; incidence peaks at ages 10 to 12 years. Like other extragonadal germ cell tumors, CNS variants hug the midline; 80% or more arise in structures around the third ventricle, with the area of the pineal gland their most common site of origin followed by the suprasellar compartment.
The histologic types of germ cell tumors include germinoma, teratoma (mature, immature, and with malignant transformation), yolk sac tumor, embryonal carcinoma, and choriocarcinoma. No WHO histologic grades are available for these types of tumors. An increased risk of intracranial germ cell tumor is associated with Klinefelter syndrome (47 × YY) and a variety of anomalies that include testicular atrophy, gynecomastia, eunuchoid habitus, and elevated serum gonadotrophins.[46,47,48] Cytogenetically, chromosome 12 abnormalities and aneuploidy appear to delineate a group of germ cell tumors harboring primordial germ cell-like elements (e.g., germinoma or seminoma) from pure teratomas and yolk sac tumors of congenital or infantile onset. No specific molecular genetics exist with these types of tumors.
Most localized germinomas can be cured with radiation therapy alone, and they have 5-year survival rates ranging from 65% to 95%. Patients with germ cell tumors of other histologic types do not fare as well, except for those who can tolerate gross total resection of mature teratomas, which tend to be noninvasive and amenable to complete excision.
(Refer to the Germ Cell Tumors section of this summary for treatment information. Refer to the PDQ summary on Childhood Brain and Spinal Cord Tumors Treatment Overview for more information.)
Tumors of the sellar region
Pituitary tumors occur most frequently in the sellar region, but they are traditionally grouped separately. (Refer to the PDQ summary on Pituitary Tumor Treatment for more information.) Granular cell tumors and chordomas are also found.