What is Most common tumor of pineal gland is: and explain in detail?
Ans: B (Germinomas) Ref: Robbia's Pathologic Basis of Disease, 8th ed, Pg: 1163Explanation:PINEAL GLANDThe rarity of clinically significant lesions (virtually only tumors) justifies brevity in the consideration of the pineal gland.It is a minute, pinecone-shaped organ , weighing 100 to 180 mg and lying between the superior colliculi at the base of the brain.It is composed of a loose, neuroglial stroma enclosing nests of epithelialappearing pineocytes, cells with photosensory and neuroendocrine functions (hence the designation of the pineal gland as the "third eye").Silver impregnation stains reveal that these cells have long, slender processes reminiscent of primitive neuronal precursors intermixed with the processes of astrocytic cells.The principal secretory product of the pineal gland is melatonin, which is involved in the control of circadian rhythms, including the sleep-wake cycle; hence the poputar use of melatonin for the treatment of jet lag.All tumors involving the pineal are rareMost (50% to 7(1 %) arise from sequestered embryonic germ cells.They most commonly take the form of so-called germinomas. resembling testicular seminoma or ovarian dysgerminoma.Other lines of germ cell differentiation include embryonal carcinomas, choriocarcinomas, mixtures of germinoma. embryonal carcinoma, and choriocarcinoma, typical teratomas (usually benign).Whether to characterize these germ cell neoplasms as pinealomas is still a subject of debate, but most "pinealophiles" favor restricting the term pinealoma to neoplasms arising from the pineocytes.