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SUMMARY Seven cases of clinically symptomatic benign glial cyst of the pineal gland are reported. The cysts' size ranged from 1 0-4 5 cm in diameter. They were characterised by a golden or, less frequently, brown-reddish proteinaceous or haemorrhagic fluid content. The cyst wall, up to 2 mm thick, consisted of clusters of normal pineal parenchymal cells, often compressed and distorted, surrounded by reactive gliotic tissue which sometimes contained Rosenthal fibres. The presenting clinical features included headache (6/7), signs of raised intracranial pressure, partial or complete Parinaud's syndrome (5/7), cerebellar deficits (2/7), corticospinal and corticopontine fibre (2/7) or sensory (1/7) deficits, and emotional disturbances (2/7). CT and MRI (in 2/7 cases) scans showed a hypodense or nonhomogeneous lesion in the region of the pineal gland, with or without contrast enhancement. Surgical excision resulted in complete clearance of the symptoms in 5/7 patients. The previous literature is reviewed and the clinicopathological correlations and the possible pathogenetic mechanisms are discussed. The need to distinguish this benign lesion from other mass lesions of the pineal region, in particular from pinealocytoma, is stressed.Lesions of the pineal region comprise germinomas, teratomas, tumours arising from the pineal parenchyma such as pineocytomas and pineoblastomas, gliomas, and cysts, including epidermoid, dermoid, arachnoid and glial cysts. Small benign glial cysts of the pineal gland are a common incidental finding in adults, discovered on CT scanning and on post-mortem examination; they are usually less than 0 5 cm in diameter and, unlike the other lesions mentioned above, do not give rise to symptoms. Large, symptomatic pineal cysts of the same nature have been described only rarely. We have studied seven such cases over the last five years. Their clinical and pathological features are presented in this report. Materials and methodsThe cases described in this report were referred by other pathologists to one of us (LJR) for consultation on histological diagnosis. They are seven out of about 1500 consultation cases seen consecutively at

(4A0078) cells including their dendrites, and the climbing fibers that formed synapses Materials and Methods Male and female 1295v mice (courtesy of Dr.

The neuropathological features of 22 autopsied cases of NF have been reviewed, with special reference to the malformative and proliferative lesions implicating the intracranial and intraspinal neural structures. Eleven cases represented examples of the central form of the disease, and 11 examples of the peripheral form. The central form is defined by the association and multiplicity of cranial and spinal meningeal, nerve-sheath, and glial neoplasms (astrocytomas and ependymomas). Bilateral acoustic schwannomas are a frequent, but not invariable, component of the disease. Central NF is also characterized by the very frequent incidence (9 out of 11 cases) of distinctive malformative CNS lesions, which included intramedullary and perivascular schwannosis, meningioangiomatosis, discrete ependymal ectopias, atypical glial cell nests in the grey matter, and, less frequently, syringomyelia. Many of these hamartomatous changes were closely associated topographically with florid neoplastic lesions. Five of the 11 cases of peripheral NF showed involvement of the CNS by cellular proliferative changes that included subependymal gliofibrillary nodules in 3 cases (causing aqueduct stenosis in 2, with resulting hydrocephalus in 1); hyperplastic meningioencephalic gliosis involving the pons and the cerebellum in 1 case; and micronodular capillary and arteriolar proliferations typical of the vascular form of NF in 1 case. Whereas some of the glial proliferations are probably hamartomatous in nature, others may represent an abnormal productive neuroglial response to adjacent pathological conditions, such as antecedent cerebral hemorrhage or infarct, known to stimulate a proliferative gliosis. Such a response may exhibit morphological features that are indistinguishable from those of an astrocytoma, including leptomeningeal and perivascular invasion. The incidence of proliferative CNS lesions in both the central and the peripheral form of NF indicates that the spectrum of tissues implicated extends beyond those derived solely from the neural crest.

Using a four-step immunoperoxidase (PAP) method and the monoclonal antibody MAbA9-C6 (MAbA9-C6), which defines an epitope of the retinal S-antigen (S-Ag), we investigated the S-Ag immunoreactivity in human fetal, newborn, infantile and adult pineal glands and in 13 human pineal parenchymal tumors. S-Ag immunoreactivity was demonstrated in a few cells in one of the four fetal and in both infantile glands. Eight of nine adult pineal glands contained isolated MAbA9-C6-positive cells. In two of seven pineocytomas showing neuronal or gangliogliomatous differentiation a few scattered cells displayed S-Ag positivity; two of four pineoblastomas contained small groups of strongly immunoreactive neoplastic cells; two malignant pineocytomas did not demonstrate any S-Ag immunoreactivity. Our results indicate that isolated cells in human pineal gland retain some of the cytochemical characteristics of photoreceptor cells recognized by the MAbA9-C6, and that S-Ag immunoreactivity may be occasionally expressed in pineal parenchymal tumors.