Craniopharyngioma, light micrograph. Craniopharyngioma is a燱HO Grade 1 epithelial tumour爑sually seen in the爏ellar/suprasellar region. It arises most likely from the爎emnants of Rathke's pouch. Some cases may have their origin in爉isplaced odontogenic rests along pituitary stalk. Grossly, they are often爏olid and cystic with areas of calcification. Craniopharyngiomas are subdivided into two types based on morphologic features: 1) Adamantinomatous (90% of cases) seen mostly in children and 2) Papillary (10% of cases) seen mostly in adults. The image shows adamantinomatous type with most of the key diagnostic features: a) sheets of squamous epithelial cells with peripheral palisading (which is best seen along the top of the image); b) a loose meshwork of epithelial cells called the stellate reticulum; c) nodules of anucleated squames (ghost cells) with brightly eosinophilic cytoplasm termed wet keratin. Wet keratin is considered diagnostic even in the absence of viable epithelium.