Neuroendocrine aspects of pineal tumors.

The evaluation and treatment of pineal region tumors has changed dramatically in the past decade. New imaging techniques result in earlier diagnosis. Surgical techniques now permit removal of benign tumors (about one third of cases). Pathologic diagnosis is obtained for the remainder, and postoperative therapy can be planned rationally. Germ cell tumors pose a particularly difficult problem for the pathologist because they often contain mixed germ cell elements. Biologic markers, beta HCG and AFP, aid diagnosis and can be monitored in serum and CSF to assess response to treatment. Only boys develop precocious puberty with pineal tumors. What appears to be puberty is actually pseudoprecocious puberty, due to ectopic production of HCG by their neoplasms (choriocarcinomas or germinomas with syncytiotrophoblastic giant cells). HCG can stimulate tests to produce testosterone, but FSH is necessary (together with LH or HCG) to stimulate ovaries to produce estrogen. Diabetes insipidus with pineal tumors is usually due to spread to the hypothalamus by ventricular seeding, but we report a case of aqueductal stenosis with diabetes insipidus resulting from a massively dilated third ventricle. Rarely, hydrocephalus may trigger true precocious puberty, a syndrome easily differentiated from pseudoprecocious puberty by endocrinologic tests. There are no biologic markers to diagnose pineal parenchymal tumors. Elevation of melatonin in plasma or CSF and increased tumor biosynthetic activity has been reported in isolated cases, but the range of melatonin values in normals is very wide, and melatonin levels do not correlate with specific pathologic tumor types. Both parenchymal and nonparenchymal tumors may increase melatonin nonspecifically by interfering with regulatory mechanisms of the normal pineal gland.