Crniopharyngiomas

Diagnosis Pathology Surgical Treatment Radiation Shunting Results

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Introduction

Controversy has surrounded the craniopharyngiomas as it has almost no other tumor affecting the brain; the origin, natural history, operative removability, response to radiation, and optimal therapy of the lesion have all been topics of debate. Many of these questions remain unresolved, and the conclusions must be regarded as only tentative.

Origin

At the end of the nineteenth century, pathologists were intrigued by a strange group of epithelial tumors encountered above and within the sella turcica. Mott and Barrett, in 1899, postulated that these tumors might arise from the hypophyseal duct or Rathke's pouch. This amazingly prescient theory, based on three cases of third-ventricular tumor, continues to be widely held. Histologic characteristics of these tumors were well described in 1904 by Erdheim, who pointed out similarities between craniopharyngiomas and adamantinomas, tumors known to be primitive neoplasms of buccal origin. He thought this close resemblance proved that craniopharyngiomas arose from ectoblastic remnants of Rathke's duct. In addition, the anterior wall of Rathke's pouch forms both the pars tuberalis and the anterior lobe of the pituitary, the most common sites for craniopharyngiomas. Since that time, craniopharyngiomas have been found along the path of development of Rathke's pouch from the pharynx to the floor of the sella, as well as above and within the sella.
However, while craniopharyngiomas and adamantinomas have a similar appearance, the histologic picture differs greatly between a Rathke's cleft cyst and a craniopharyngioma, although these entities are postulated to have a common origin. The Rathke's cleft cyst may be a simple cystic enlargement and may lack the changes induced by neoplastic transformation found in craniopharyngiomas.
Some investigators have demonstrated histologic differences between adult and childhood craniopharyngiomas that might indicate separate origins. They stress that almost half the adult tumors are made up of squamous epithelium, often with a papillary form, without palisading or other adamantinomatous characteristics of the childhood tumor. These differences are not confirmed in some series. In one series 17 percent of patients had the papillary type of tumor; these patients ranged in age from 26 to 54 years. In the same series, adamantinomatous tumors were found in patients ranging in age from I to 69 years. Other workers have tried to predict the behavior and clinical likelihood of recurrence on the basis of these pathologic differences and have found that both the outcome of surgery and the recurrence rate were slightly better for papillary tumors than for the adamantinomatous variety.
Squamous epithelial rests in the hypophysis were described in autopsy material by Carmichael more than 70 years ago. However, these cell rests are found in only 3 percent of neonates and are found with increasing frequency in each succeeding decade. This finding suggests that an embryonic origin need not be postulated for such cells, which may appear later in life because of cellular alteration or metaplasia of pituitary cells, which are also of ectodermal origin.

Incidence


Craniopharyngiomas are variously reported to constitute between 2.5 and 4 percent of all brain tumors. Since almost half these tumors occur in childhood, their incidence in children is higher; they constituted 9 percent of Matson' s series of childhood tumors, in which craniopharyngioma was the most common nonglial tumor. When the differential diagnosis is limited to tumors of the sellar-chiasmatic region, craniopharyngiomas constitute a majority in children (54 percent) but only 20 percent in adults. However, craniopharyngiomas may become symptomatic at any age, with the oldest in this series being 71 at the time of operation. The tumor occurs with equal frequency in both sexes throughout life. Although a male preponderance in children has been reported, it is not supported by other reports of large series of children with equal sex distribution.

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