Craniopharyngiomas are epithelial tumors that usually arise in the pituitary stalk adjacent to the optic chiasm. On gross pathology, craniopharyngiomas are cystic or partially cystic with solid areas.The cyst is filled with a turbid, proteinaceous material of brownish-yellow color that glitters and sparkles because of a high content of floating cholesterol crystals. On microscopic histopathology, it is categorized into two subtypes: Adamantinomatous and papillary.

• Craniopharyngioma is a nonglial intracranial tumor derived from a malformation of embryonic tissue. ^[1]
• There are differing hypotheses on its embryonic origin.
• Pathogenesis of craniopharyngioma is not completely understood.
• Some authorities advocate that it originates from ectodermal remnants of Rathke’s pouch. ^[2]
• Few pathologists believe that it originates from residual embryonal epithelium of the anterior pituitary gland and of the anterior infundibulum.

• According to this theory, craniopharyniomas arise from neoplastic transformation of embryonic squamous cell nests of Rathke’s pouch with the stomodeum.^[3]
• Cell remnants of the craniopharyngeal duct are spread through the intrasellar and suprasellar region.
• The rotation of the adenohypophysis is caused by different rates of cellular multiplication.
• Different rates of cellular multiplication results in a spread of cells of the craniopharyngeal duct to the suprasellar region.
• The rare location at the cerebellopontine angle could fit with this hypothesis.

• Papillary craniopharyngiomas are the result of metaplasia of the adenohypophyseal cells in the anterior pituitary.
• This theory is supported by the presence of metaplastic nests in the gland.^[2]

• On macroscopic examination, craniopharyngiomas are cystic or partially cystic with solid areas.^[4]
• Craniopharyngiomas can arise anywhere along the craniopharyngeal canal.
• It occur most often in sellar or suprasellar region but can have anterior extension to the prechiasmatic cistern and subfrontal spaces.^[4]
• Posterior extension into the prepontine , third ventricle, posterior fossa, and foramen magnum; and laterally toward the subtemporal spaces.
• Rare locations of craniopharyngiomas are; the nasopharynx , paranasal area , sphenoid bone, ethmoid sinus, intrachiasmatic area, temporal lobe.
• Craniopharyngiomas are supplied with blood coming from the anterior cerebral circulation.^[5]
• Several inflammatory cytokines have been shown to be elevated in the craniopharyngioma cyst fluid compared with cerbrospinal fluid (CSF).^[6]
• Tumor adhesion is the result of local inflammation.

• The histologic pattern consists of nesting of squamous epithelium bordered by radially arranged cells.
• Tumor is frequently accompanied by calcium deposition and have a microscopic papillary architecture.^[3]
• Two distinct types are recognized:^[7][8]

1. Adamantinomatous craniopharyngioma
2. Papillary craniopharyngioma

• In the adamantinomatous type, calcifications are visible on neuroimaging and are helpful in diagnosis.
• The papillary type rarely calcifies. On light microscopy, the cysts are seen to be lined by stratified squamous epithelium.
• Keratin pearls may also be seen.
• The cysts are usually filled with a yellow, viscous fluid which is rich in cholesterol crystals.
• Islands of densely packed cells merge with loosely cohesive aggregates of squamous cells known as stellate reticulum.
• Nodules of “wet keratin” representing remnants of pale nuclei embedded within an eosinophilic keratinous mass may be found.
• Cystic cavities containing squamous debris are lined by flattened epithelium.
• Granulomatous inflammation associated with cholesterol clefts and giant cells may be detectable, but this is more typical for xanthogranuloma.^[2]
• Piloid gliosis with abundant Rosenthal fibers is often seen at the infiltrative interface of the tumor and should not be mistaken for pilocytic astrocytoma.
• Malignant transformation of craniopharyngioma appears to be very rare.

• Multiple chromosomal abnormalities have been reported by classic cytogenetic analysis.
• Most tumors had abnormalities involving chromosomes 2 and 12.
• More than 70% of adamantinomatous craniopharyngiomas harbor a mutation of the β-catenin gene.
• Most of the mutations affect exon 3, which encodes the degradation targeting box of β-catenin.
• No mutations have been demonstrated in papillary craniopharyngioma.
• Comparative genomic hybridization studies on two large series of craniopharyngiomas have failed to show significant chromosomal imbalances.
• The mutations of genes encoding β-catenin (CTNNB1 and APC) are an exclusive characteristic of adamantinomatous craniopharyngioma.
• Few researchers demonstrated a causative effect of mutant β-catenin in the etiology of human adamantinomatous craniopharyngioma.

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