THE ECTOPIC pinealoma is a distinct entity because of the diagnostic and therapeutic problems it presents. From the diagnostic point of view, a readily distinguishable neuroendocrinologic triad of signs is evident in most presentations. Because of the rarity of the lesion, the prodromal symptomatology remains unrecognized until the full-blown syndrome unfolds. The therapeutic aspects of management are as intriguing as the diagnostic problems. Unfortunately, in many cases the inability to diagnose this entity properly has precluded definitive treatment. The literature has not emphasized its curability by radiotherapy, despite the fact that all survivors reported were so treated. The loss of patients resulting from neuroendocrine complications is of equal importance. Since this situation can be remedied, it is essential to be aware of the evolution of the clinical course of ectopic pinealomas. Review of Literature A detailed tabulation of 36 cases is presented. Table I elaborates upon 28 cases reported in the literature. Eight previously unpublished cases are summarized in Table II. In an equal number not presented here, the chiasmal region has been involved, secondary to metastases from a primary pinealoma of the pineal body. Pathogenesis The pineal body, located in the posterior portion of the third ventricle, is a structure whose function remains beyond definition. Krabbe (1923) indicated that the pineal was not essential either to the maintenance of life or to sexual development, although related to the latter. It is described as consisting of pineal cells, connective tissue, glial cells, and nerve cells. Calcium deposits form with time and age. Globus and Silbert (1931) described the various patterns of histology in different developmental stages in a study of the pineal bodies in subjects of various ages. Del Rio-Hortega (1932) found the normal cytology confusing because the two main cell types vary in both size and shape and because there are usually different amounts of neuroglial connective tissue. The pathogenesis of tumors believed to originate from this source remains confusing in an organ with so many variations, the significance of which are unknown. Russell (1944) postulated that a relationship existed between pinealomas and teratomas. In the classic description, the pinealoma is composed of solid masses of large spheroidal cells separated into islands by stroma. This stroma is infiltrated in many places by numerous small lymphocyte-like cells. The large spheroidal cells are considered to be neural in origin; they resemble a developmental phase in which the pineal cells are arranged in a mosaic. In serial sectioning of typical pinealomas, Russell (26) disclosed a variety of tissues which were, perhaps, confined to relatively small areas of the tumor. These included tubules lined with columnar, mucus-secreting epithelium, cartilaginous tissue, and even striped muscle.