Oncocytic and granular cell neoplasms of the central nervous system and pituitary gland

Oncocytic transformation is an infrequent event within the central nervous system and is limited to neoplasms of the choroid plexus, meninges, and pit uitary gland. Oncocytic modifications in choroid plexus tumors seem to occu r predominantly in adult patients and in the fourth ventricle and do not se em to reflect any particular biological behavior, Meningiomas showing oncoc ytic differentiation have been recently described and this variant probably behaves more aggressively. Pituitary oncocytomas are regarded as a subtype of null cell adenomas. Oncocytic tumors have a significantly higher risk o f progression with a higher recurrence rate after radiotherapy. Oncocytic c hanges in astrocytic neoplasms are rare, More frequently, astrocytomas can show granular changes that result in neoplasms composed of cells with granu lar cytoplasm and eccentric nuclei resembling foamy macrophages. Granular c ell astrocytomas may mimic non-neoplastic lesions such as cerebral infarcti on and demyelinating disease. Cells with granular bodies are frequent in pi locytic astrocytoma, pleomorphic xanthoastrocytoma, and ganglion cell tumor s, Their presence is considered a useful diagnostic finding to distinguish these low-grade lesions from malignant gliomas, A rare neoplasm is the gran ular cell tumor of the infundibulum that, when symptomatic, has to be diffe rentiated from pituitary adenomas and other more common lesions of the sell ar region, Copyright (C) 1999 by W.B. Saunders Company.