Germ cell tumors masquerading as central nervous system sarcoidosis.

The diagnosis of central nervous system sarcoidosis is uncertain without typical multisystem involvement. We describe two patients with isolated central nervous system mass lesions whose biopsy results were consistent with sarcoidosis. After a progressive clinical course, they were found to have diencephalic germinomas. Germ cell tumors, in particular, should be considered in the differential diagnosis of central nervous system sarcoidosis as they are potentially treatable, occur in intracranial locations favored by sarcoidosis mass lesions, and may be surrounded by granulomatous inflammation that can be mistaken for the noncaseating granulomas of sarcoidosis.