Cytologic diagnosis of intracranial germinomas in smear preparations.

Although cytologic smear preparations have been used in the intraoperative diagnosis of central nervous system tumors for a long time, detailed descriptions of the rarer tumors, including germinomas, have not been provided in the literature. We reviewed the cytologic features of five intracranial germinomas diagnosed with the smear technique. The smears showed sheets of large tumor cells intimately mixed with mature lymphocytes. The cells had delicate, vacuolated cytoplasm with distinct borders, while the nucleoli were prominent and elongated. There often was an amorphous, eosinophilic background of extracellular matrix. The main differential diagnoses were true pineal gland tumors, pituitary adenomas, craniopharyngiomas, pilocytic astrocytomas and parasellar meningiomas.